fix(frontend): Propagate API auth errors to original requestor (#10716)

- Resolves #10713

### Changes 🏗️

- Remove early exit in API proxy that suppresses auth errors
- Remove unused `proxy-action.ts`

### Checklist 📋

#### For code changes:
- [x] I have clearly listed my changes in the PR description
- [x] I have made a test plan
- [x] I have tested my changes according to the test plan:
  - [x] Publish Agent dialog works when logged out
  - [x] Publish Agent dialog works when logged in

---------

Co-authored-by: Nicholas Tindle <nicholas.tindle@agpt.co>

autogpt_platform/autogpt_libs/autogpt_libs/auth/middleware.py

@@ -10,8 +10,8 @@ from starlette.status import HTTP_401_UNAUTHORIZED
 from .config import settings
 from .jwt_utils import parse_jwt_token
 
-security = HTTPBearer()
 logger = logging.getLogger(__name__)
+bearer_auth = HTTPBearer(auto_error=False)
 
 
 async def auth_middleware(request: Request):
@@ -20,11 +20,10 @@ async def auth_middleware(request: Request):
         logger.warning("Auth disabled")
         return {}
 
-    security = HTTPBearer()
-    credentials = await security(request)
+    credentials = await bearer_auth(request)
 
     if not credentials:
-        raise HTTPException(status_code=401, detail="Authorization header is missing")
+        raise HTTPException(status_code=401, detail="Not authenticated")
 
     try:
         payload = parse_jwt_token(credentials.credentials)