chore: post-deployment cleanup and docs update

- Make AI routing rules DB-driven (read from system_configs, removed from config.py)
- Add translation quota tracking to LLM translation (OpenAIProvider)
- Add Alibaba MT ECS RAM role support (STS token, no AccessKey needed)
- Fix admin sidebar link for AI模型配置 page
- Fix Quota.vue API path (quotas → translation-quotas)
- Fix login auto-redirect to dashboard
- Add provider dropdown selects to AI routing config UI
- Clean up stale ai_provider_* system_configs records
- Remove OpencodeGo, Spark providers (code + DB)
- Update deploy config: nginx port 8000, systemd cwd

backend/app/ai/providers/openai.py

@@ -51,6 +51,20 @@ class OpenAIProvider(AIProvider):
         self._cheap_model = "gpt-4o-mini" if model == "gpt-4o" else model
 
     async def translate(self, text: str, source_lang: Optional[str], target_lang: str, context: Optional[str] = None) -> Dict[str, Any]:
+        from app.services.translation_quota import TranslationQuotaService
+        from app.database import AsyncSessionLocal
+
+        async with AsyncSessionLocal() as db:
+            quota_svc = TranslationQuotaService(db)
+            if not await quota_svc.check_quota("llm"):
+                raise Exception("LLM translation quota exhausted or disabled")
+            result = await self._do_translate(text, source_lang, target_lang, context)
+            if result and result.get("translated_text"):
+                await quota_svc.consume("llm", len(text))
+                await db.commit()
+            return result
+
+    async def _do_translate(self, text: str, source_lang: Optional[str], target_lang: str, context: Optional[str] = None) -> Dict[str, Any]:
         system = SYSTEM_PROMPTS["translate"]
         if context:
             system += f"\nContext: this is about {context}"