Refactor document handling and update Milvus collection settings

- Removed multiple failed document entries from `documents.json`.
- Added a new document entry with updated metadata and changed the index name to `regulations_dense_1024_v2`.
- Updated architecture documentation to reflect changes in the Milvus collection name.
- Adjusted requirements by removing the sqlalchemy dependency.
- Modified test cases to align with new document structure and naming conventions.
- Introduced a new test file for Milvus vector index runtime recovery and error handling.
- Updated assertions in various test files to ensure compatibility with the new schema.

backend/app/api/main.py

@@ -3,6 +3,7 @@
 from contextlib import asynccontextmanager
 
 from fastapi import FastAPI, Request
+from fastapi.encoders import jsonable_encoder
 from fastapi.middleware.cors import CORSMiddleware
 from fastapi.responses import JSONResponse
 from loguru import logger
@@ -12,6 +13,7 @@ from app.api.routes import api_router
 from app.config.logging import setup_logging
 from app.config.settings import settings
 from app.shared.bootstrap import cleanup_runtime_dependencies, preload_runtime_dependencies
+from app.shared.errors import VectorStoreSchemaError
 # Keep module behavior explicit so the backend flow stays easy to audit.
 
 
@@ -55,16 +57,33 @@ app.add_middleware(
 app.include_router(api_router, prefix="/api/v1")
 
 
+@app.exception_handler(VectorStoreSchemaError)
+async def vector_store_schema_exception_handler(request: Request, exc: VectorStoreSchemaError):
+    """Return a stable JSON response for vector store schema/runtime errors."""
+    logger.error(f"向量库 schema 异常: {exc}")
+    return JSONResponse(
+        status_code=500,
+        content=jsonable_encoder(
+            ErrorResponse(
+                error="VectorStoreSchemaError",
+                message=str(exc),
+            )
+        ),
+    )
+
+
 @app.exception_handler(Exception)
 async def global_exception_handler(request: Request, exc: Exception):
     """Global exception handler."""
     logger.error(f"未处理的异常: {exc}")
     return JSONResponse(
         status_code=500,
-        content=ErrorResponse(
-            error="InternalServerError",
-            message=str(exc),
-        ).model_dump(),
+        content=jsonable_encoder(
+            ErrorResponse(
+                error="InternalServerError",
+                message=str(exc),
+            )
+        ),
     )