feat(legal): add CLA with automated GitHub Actions enforcement

Introduce Individual Contributor License Agreement (ICLA) to enable
dual licensing (LGPL-V3 open source + future closed-source releases).

- CLA.md: Apache ICLA-style license grant with moral rights waiver,
  patent license, electronic signature clause, and assignability
- .github/workflows/cla.yml: CLA Assistant Lite bot that auto-checks
  PRs, posts signing prompts, and stores signatures on a separate
  `cla-signatures` branch to keep main branch history clean

.github/workflows/cla.yml

+name: "CLA Assistant"
+
+on:
+  issue_comment:
+    types: [created]
+  pull_request_target:
+    types: [opened, reopened, closed, synchronize]
+
+permissions:
+  actions: write
+  contents: write
+  pull-requests: write
+  statuses: write
+
+jobs:
+  cla-check:
+    if: |
+      github.event_name == 'issue_comment' ||
+      (github.event_name == 'pull_request_target' && github.event.action != 'closed')
+    runs-on: ubuntu-latest
+    steps:
+      - name: "CLA Assistant"
+        if: |
+          (github.event.comment.body == 'recheck' ||
+           github.event.comment.body == 'I have read the CLA Document and I hereby sign the CLA') ||
+          github.event_name == 'pull_request_target'
+        uses: contributor-assistant/github-action@v2.6.1
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          path-to-signatures: "cla.json"
+          path-to-document: "https://github.com/Wei-Shaw/sub2api/blob/main/CLA.md"
+          branch: "cla-signatures"
+          allowlist: "dependabot[bot],renovate[bot],bot*"
+          lock-pullrequest-aftermerge: false
+          custom-notsigned-prcomment: |
+            Thank you for your contribution! Before we can merge this PR, we need $you to sign our [Contributor License Agreement (CLA)](https://github.com/Wei-Shaw/sub2api/blob/main/CLA.md).
+
+            **To sign**, please reply with the following comment:
+
+            > I have read the CLA Document and I hereby sign the CLA
+
+            You only need to sign once — it will be valid for all your future contributions to this project.
+          custom-pr-sign-comment: "I have read the CLA Document and I hereby sign the CLA"
+          custom-allsigned-prcomment: "All contributors have signed the CLA. ✅"
+
+  cla-lock:
+    if: github.event_name == 'pull_request_target' && github.event.action == 'closed' && github.event.pull_request.merged == true
+    runs-on: ubuntu-latest
+    steps:
+      - name: "Lock merged PR"
+        uses: contributor-assistant/github-action@v2.6.1
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          path-to-signatures: "cla.json"
+          path-to-document: "https://github.com/Wei-Shaw/sub2api/blob/main/CLA.md"
+          branch: "cla-signatures"
+          lock-pullrequest-aftermerge: true

CLA.md

+# Sub2API Individual Contributor License Agreement (v1.0)
+
+Thank you for your interest in contributing to Sub2API ("the Project"). This Contributor License Agreement ("Agreement") documents the rights granted by contributors to the Project.
+
+By signing this Agreement, you accept and agree to the following terms and conditions for your present and future contributions submitted to the Project.
+
+## 1. Definitions
+
+- **"You" (or "Your")** means the copyright owner or legal entity authorized by the copyright owner that is making this Agreement.
+- **"Contribution"** means any original work of authorship, including any modifications or additions to an existing work, that is intentionally submitted by You to the Project for inclusion in, or documentation of, any of the products owned or managed by the Project. For the purposes of this definition, "submitted" means any form of electronic, verbal, or written communication sent to the Project or its representatives, including but not limited to communication on electronic mailing lists, source code control systems, and issue tracking systems that are managed by, or on behalf of, the Project for the purpose of discussing and improving the Project, but excluding communication that is conspicuously marked or otherwise designated in writing by You as "Not a Contribution."
+- **"Project Owner"** means Wesley Liddick, or any individual or legal entity to whom Wesley Liddick has explicitly assigned or transferred ownership of the Project in writing, and their respective successors and assigns.
+
+## 2. Grant of Copyright License
+
+Subject to the terms and conditions of this Agreement, You hereby grant to the Project Owner a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Your Contributions and such derivative works. This license includes, without limitation, the right to sublicense, assign, and transfer these rights to any third party, including without limitation any successor, assignee, or acquiring entity of the Project or the Project Owner, and to use Your Contributions under any license, including proprietary or commercial licenses.
+
+## 3. Moral Rights
+
+To the fullest extent permitted by applicable law, You irrevocably waive and agree not to assert any moral rights (including rights of attribution and integrity) that You may have in Your Contributions, and agree that the Project Owner and its licensees may use, modify, and distribute Your Contributions without attribution or other obligations arising from moral rights.
+
+## 4. Grant of Patent License
+
+Subject to the terms and conditions of this Agreement, You hereby grant to the Project Owner a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable patent license to make, have made, use, offer to sell, sell, import, and otherwise transfer Your Contributions, where such license applies only to those patent claims licensable by You that are necessarily infringed by Your Contribution(s) alone or by combination of Your Contribution(s) with the Project to which such Contribution(s) was submitted.
+
+## 5. Representations and Warranties
+
+You represent and warrant that:
+
+(a) You are legally entitled to grant the above licenses.
+
+(b) If Your employer(s) has rights to intellectual property that You create that includes Your Contributions, You have received permission to make Contributions on behalf of that employer, or that Your employer has waived such rights for Your Contributions to the Project.
+
+(c) Each of Your Contributions is Your original creation, or You have sufficient rights to submit it under the terms of this Agreement. You agree to provide, upon request, reasonable documentation or explanation of any third-party materials included in Your Contributions.
+
+## 6. No Warranty
+
+Your Contributions are provided on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. You are not expected to provide support for Your Contributions, except to the extent You desire to provide support.
+
+## 7. No Obligation
+
+You understand that the decision to include Your Contribution in any product or project is entirely at the discretion of the Project Owner, and this Agreement does not obligate the Project Owner to use Your Contribution.
+
+## 8. Retention of Rights
+
+You retain ownership of the copyright in Your Contributions. This Agreement does not transfer any copyright or other intellectual property rights from You to the Project Owner. This Agreement only grants the licenses described above.
+
+## 9. Term and Termination
+
+This Agreement shall remain in effect indefinitely. You may terminate this Agreement prospectively by providing written notice to the Project Owner, but such termination shall not affect the licenses granted for Contributions submitted prior to the effective date of termination. The licenses granted herein for Contributions submitted prior to termination are perpetual and irrevocable.
+
+## 10. Electronic Signature
+
+You agree that Your electronic signature (including but not limited to typing a specific phrase in a pull request, issue, or other electronic communication) is legally binding and has the same force and effect as a handwritten signature. You consent to the use of electronic means to enter into this Agreement and acknowledge that this Agreement is enforceable as if executed in a traditional written format.
+
+## 11. General Provisions
+
+**Entire Agreement.** This Agreement constitutes the entire agreement between You and the Project Owner with respect to Your Contributions and supersedes all prior or contemporaneous understandings regarding such subject matter.
+
+**Severability.** If any provision of this Agreement is held to be unenforceable or invalid, that provision will be enforced to the maximum extent possible and the remaining provisions will remain in full force and effect.
+
+**No Waiver.** The failure of the Project Owner to enforce any provision of this Agreement shall not constitute a waiver of that provision or any other provision.
+
+**Amendment.** This Agreement may only be modified by a written instrument signed by both parties. Modifications to this Agreement apply only to Contributions submitted after the modified Agreement is published and accepted by You. Prior Contributions remain governed by the version of the Agreement in effect at the time of submission.
+
+**Notification.** Notices under this Agreement shall be sent to the Project Owner via a GitHub issue on the Project repository. Notices are effective upon receipt.
+
+---
+
+**By signing this CLA, you acknowledge that you have read and understood this Agreement and agree to be bound by its terms.**
+
+To sign, reply in the pull request with:
+
+> I have read the CLA Document and I hereby sign the CLA