feat: Implement initial backend indexer for vaults, supporting file system scanning, markdown parsing, and in-memory metadata indexing.

backend/indexer.py

@@ -304,7 +304,8 @@ async def build_index(progress_callback=None) -> None:
     Notifies progress via the provided callback.
     """
     global index, vault_config
-    vault_config = load_vault_config()
+    vault_config.clear()
+    vault_config.update(load_vault_config())
     
     global _index_generation
     with _index_lock:

backend/main.py

@@ -604,7 +604,7 @@ async def api_vaults(current_user=Depends(require_auth)):
     result = []
     for name, data in index.items():
         if "*" in user_vaults or name in user_vaults:
-            v_type = vault_config.get(name, {}).get("type", "VAULT")
+            v_type = data.get("config", {}).get("type", "VAULT")
             result.append({
                 "name": name,
                 "file_count": len(data["files"]),