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/tests/test_config.py

@@ -14,11 +14,12 @@ class TestConfig:
         assert settings.REFRESH_TOKEN_EXPIRE_DAYS == 30
 
     def test_ai_routing_config(self):
-        assert "translate" in settings.AI_ROUTING
-        assert "reply" in settings.AI_ROUTING
-        assert "marketing" in settings.AI_ROUTING
-        assert "extract" in settings.AI_ROUTING
-        assert "primary" in settings.AI_ROUTING["translate"]
+        from app.ai.router import DEFAULT_ROUTING
+        assert "translate" in DEFAULT_ROUTING
+        assert "reply" in DEFAULT_ROUTING
+        assert "marketing" in DEFAULT_ROUTING
+        assert "extract" in DEFAULT_ROUTING
+        assert "primary" in DEFAULT_ROUTING["translate"]
 
     def test_free_tier_limits(self):
         assert settings.FREE_DAILY_TRANSLATE_CHARS == 5000