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/core/config.py

@@ -27,7 +27,7 @@ class Settings(BaseSettings):
     # Milvus
     milvus_host: str = "6.86.80.8"
     milvus_port: int = 19530
-    milvus_collection: str = "regulations_dense_1024_v1"
+    milvus_collection: str = "regulations_dense_1024_v2"
 
     # LLM / embedding defaults aligned with the migrated backend path.
     llm_model: str = "qwen-max"
@@ -47,7 +47,7 @@ class Settings(BaseSettings):
     api_port: int = 8000
 
     # Legacy aliases retained for old utility modules.
-    regulations_collection: str = "regulations_dense_1024_v1"
+    regulations_collection: str = "regulations_dense_1024_v2"
     compliance_collection: str = "compliance_cache"
 
 # Preserve the legacy module API while keeping env resolution centralized at the repo root.