Fix proper token scoping and permission enforcement

Now:
- Global tokens (aisbf.json) ONLY access global endpoints
- User tokens (database) ONLY access their own /api/u/<username> endpoints
- No cross-access possible
- Admin users still have full access

main.py

@@ -1288,6 +1288,75 @@ async def shutdown_event():
     # Cleanup multiprocessing children (sentence-transformers, torch, etc.)
     _cleanup_multiprocessing_children()
 
+# API Token Authorization Middleware
+@app.middleware("http")
+async def api_token_authorization_middleware(request: Request, call_next):
+    """Enforce proper token scope access:
+    - Global tokens (aisbf.json): CAN access global endpoints, CANNOT access user endpoints
+    - User tokens (database): CAN access ONLY their own user endpoints, CANNOT access global endpoints
+    """
+    
+    path = request.url.path
+    
+    # Skip authorization for non-API paths
+    if (path == "/" or
+        path.startswith("/dashboard") or
+        path.startswith("/auth/") or
+        path.startswith("/api/admin") or
+        path == "/favicon.ico" or
+        path.startswith("/.well-known/")):
+        return await call_next(request)
+    
+    # Skip for public models endpoints (GET only)
+    if request.method == "GET" and path in ["/api/models", "/api/v1/models"]:
+        return await call_next(request)
+    
+    is_global_token = getattr(request.state, 'is_global_token', False)
+    user_id = getattr(request.state, 'user_id', None)
+    is_admin = getattr(request.state, 'is_admin', False)
+    
+    # Admin users bypass all restrictions
+    if is_admin:
+        return await call_next(request)
+    
+    # --- USER-SPECIFIC ENDPOINTS (/api/u/*) ---
+    if (path.startswith("/api/u/") or 
+        path.startswith("/mcp/u/") or
+        path.startswith("/api/v1/u/") or
+        path.startswith("/mcp/v1/u/")):
+        
+        if is_global_token:
+            return JSONResponse(
+                status_code=403,
+                content={"error": "Global tokens cannot access user-specific endpoints. Use the user's own API token."}
+            )
+        
+        # Verify user is accessing their own endpoints
+        path_parts = path.split('/')
+        if len(path_parts) >= 4 and path_parts[2] == 'u':
+            target_username = path_parts[3]
+            
+            db = DatabaseRegistry.get_config_database()
+            authenticated_user = db.get_user_by_id(user_id)
+            
+            if not authenticated_user or authenticated_user['username'] != target_username:
+                return JSONResponse(
+                    status_code=403,
+                    content={"error": "You can only access your own user-specific endpoints."}
+                )
+    
+    # --- GLOBAL ENDPOINTS (all other API paths) ---
+    else:
+        if not is_global_token:
+            return JSONResponse(
+                status_code=403,
+                content={"error": "User tokens cannot access global endpoints. Use your user-specific endpoints at /api/u/<your-username>"}
+            )
+    
+    # All checks passed
+    return await call_next(request)
+
+
 # Authentication middleware
 @app.middleware("http")
 async def auth_middleware(request: Request, call_next):