GitLab

- Parse candidatesTokensDetails from Gemini API to separate image/text output tokens
- Add image_output_tokens and image_output_cost to usage_log (migration 089)
- Support per-image-token pricing via output_cost_per_image_token from model pricing data
- Channel pricing ImageOutputPrice override works in token billing mode
- Auto-fill image_output_price in channel pricing form from model defaults
- Add "channel_mapped" billing model source as new default (migration 088)
- Bills by model name after channel mapping, before account mapping
- Fix channel cache error TTL sign error (115s → 5s)
- Fix Update channel only invalidating new groups, not removed groups
- Fix frontend model_mapping clearing sending undefined instead of {}
- Credits balance precheck via shared AccountUsageService cache before injection
- Skip credits injection for accounts with insufficient balance
- Don't mark credits exhausted for "exhausted your capacity on this model" 429s

Gemini 2.5 Pro/Flash thinking models return thoughtsTokenCount separately
from candidatesTokenCount in usageMetadata, but this field was not parsed
or included in billing calculations, causing thinking tokens to be
unbilled.

- Add ThoughtsTokenCount field to GeminiUsageMetadata struct
- Include thoughtsTokenCount in OutputTokens across all 3 Gemini usage
  parsing paths (non-streaming, streaming, compat layer)
- Add tests covering thinking token scenarios

Closes #554

主要变更：
1. 重构代码结构：
   - 将 CleanJSONSchema 及其相关辅助函数从 request_transformer.go 提取到独立的 schema_cleaner.go 文件中，实现逻辑解耦。

2. 逻辑优化与修正：
   - 参考 Antigravity-Manager (json_schema.rs) 的实现逻辑，修正了 Schema 清洗策略。

主要变更：
1. 重构代码结构：
   - 将 CleanJSONSchema 及其相关辅助函数从 request_transformer.go 提取到独立的 schema_cleaner.go 文件中，实现逻辑解耦。

2. 逻辑优化与修正：
   - 参考 Antigravity-Manager (json_schema.rs) 的实现逻辑，修正了 Schema 清洗策略。

主要改进：
- 优化 thinking blocks 过滤策略，支持 Auto 模式降级
- 将无效 thinking block 内容转为普通 text
- 保留单个空白 text block，不过滤
- 重构配额刷新机制，统一与 Claude 一致
- 支持 cachedContentTokenCount 映射到 cache_read_input_tokens
- Haiku 模型映射到 Sonnet
- 添加 /antigravity/v1/models 端点支持
- countTokens 端点直接返回空值

- 在 GeminiUsageMetadata 添加 CachedContentTokenCount 字段
- 修正 token 映射：Gemini promptTokenCount 包含缓存，Claude input_tokens 不包含
- 流式和非流式响应均已支持

- SA1029: 创建 ctxkey 包定义类型安全的 context key
- ST1005: 错误字符串首字母改小写
- errcheck: 显式忽略 bytes.Buffer.Write 返回值
- 修复单元测试中 GatewayService 缺少 cfg 字段的问题