feat: squash merge all changes from develop-0.1.75

Squash of 124 commits from the legacy develop branch (develop-0.1.75)
onto a clean v0.1.75 upstream base, to simplify future upstream merges.

Key changes included:
- Refactor scope-level rate limiting to model-level rate limiting
- Antigravity gateway service improvements (smart retry, error policy)
- Digest session store (flat cache replacing Trie-based store)
- Client disconnect detection during streaming
- Gemini messages compatibility service enhancements
- Scheduler shuffle for thundering herd prevention
- Session hash generation improvements
- Frontend customizations (WeChat service, HomeView, etc.)
- Ops monitoring scope cleanup

frontend/src/i18n/locales/zh.ts

@@ -1492,7 +1492,6 @@ export default {
         overloaded: '过载中',
         tempUnschedulable: '临时不可调度',
         rateLimitedUntil: '限流中，重置时间：{time}',
-        scopeRateLimitedUntil: '{scope} 限流中，重置时间：{time}',
         modelRateLimitedUntil: '{model} 限流至 {time}',
         overloadedUntil: '负载过重，重置时间：{time}',
         viewTempUnschedDetails: '查看临时不可调度详情'
@@ -3232,7 +3231,6 @@ export default {
         empty: '暂无数据',
         queued: '队列 {count}',
         rateLimited: '限流 {count}',
-        scopeRateLimitedTooltip: '{scope} 限流中 ({count} 个账号)',
         errorAccounts: '异常 {count}',
         loadFailed: '加载并发数据失败'
       },