feat(billing): 支持 Fast 档位与 max 推理强度

[g1331]

Summary

补齐 GPT-5.6 max 推理强度、OpenAI Fast/Priority 处理档位和缓存写入 Token 的日志与计费支持。

Related Issue

无关联 Issue。

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Refactoring (code improvement without changing functionality)
• Tests (adding or updating tests)
• Build/CI (changes to build system or CI configuration)

Changes

• 将 max 纳入正式推理强度类型、请求日志和模型徽标。
• 分别记录请求与上游实际 service_tier，展示 Fast、Fast → Standard 和 Fast 未确认状态。
• 同步 LiteLLM Priority 单价，并按实际档位固化账单快照；未确认档位按 Standard 计费。
• 提取 Chat Completions 与 Responses 的 cache_write_tokens，接入现有缓存写入计费。
• 添加 PostgreSQL 与 SQLite 迁移及聚焦测试。

Test Plan

• Local tests pass (pnpm test:run，3576 passed / 1 skipped)
• Type check passes (pnpm exec tsc --noEmit)
• Lint passes (pnpm lint)
• Manual testing completed
• Production build passes (pnpm build)
• Drizzle artifacts are consistent (pnpm db:check:consistency)

Checklist

• Code follows the project's coding standards
• Tests have been added where necessary
• Documentation has been updated (if applicable)
• Changes do not introduce security vulnerabilities
• Commit messages follow conventions

Screenshots

未提供。日志状态徽标已通过组件测试覆盖，尚未使用包含真实 Fast 响应的本地数据进行人工截图。

Additional Notes

• 请求 Fast 但上游未返回档位时，记录为 unknown 并按 Standard 计费。
• 上游确认 Fast、但目录缺少 Priority 输入或输出单价时，记录为 price_not_found，不会静默套用 Standard 单价。
• 生产构建存在仓库原有的 Turbopack NFT 动态路径警告，与本次变更无关。

[codecov]

Codecov Report

❌ Patch coverage is 87.95181% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 72.24%. Comparing base (c18bb44) to head (fbaa9e6).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #247      +/-   ##
==========================================
+ Coverage   72.13%   72.24%   +0.10%     
==========================================
  Files         243      243              
  Lines       14152    14228      +76     
  Branches     4676     4716      +40     
==========================================
+ Hits        10209    10279      +70     
  Misses       2598     2598              
- Partials     1345     1351       +6     

Flag	Coverage Δ
verify	72.24% <87.95%> (+0.10%)	⬆️

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[g1331]

独立复审后补充提交 fbaa9e62：

• 保留手工价格的权威优先级；已确认 Fast 命中 LiteLLM Standard-only 阶梯规则时，优先尝试手工平价覆盖，否则记为 price_not_found。
• 在限流、模型拒绝、模型规则排除、普通失败、断流、流式失败与过期对账路径中保留 requestedServiceTier；没有成功响应证据时 effectiveServiceTier 保持 null。
• 补强 Responses reasoning.effort: max 与上述组合的回归测试。

本地验证：3579 tests passed / 1 skipped；Lint、Prettier、TypeScript、production build 均通过。