Restructure backend into microservices, add envelope encryption, DM files, and message editing

backend/main.py

@@ -1,7 +1,23 @@
-from constants import *
-from db import *
-from models import *
-from validation import *
-from utils import *
-from dependencies import *
-from app import *
+try:
+    # Preferred when running from project root: `python -m backend.main` or similar.
+    from backend.services.main.constants import *
+    from backend.services.main.db import *
+    from backend.services.main.models import *
+    from backend.services.main.validation import *
+    from backend.services.main.utils import *
+    from backend.services.main.dependencies import *
+    from backend.services.main.main import *
+except ModuleNotFoundError as exc:
+    # Only attempt the fallback when the missing module is the 'backend' package itself.
+    if exc.name and exc.name.startswith("backend"):
+        # Fallback when running with CWD=backend (e.g. `cd backend && uvicorn main:app`)
+        from services.main.constants import *
+        from services.main.db import *
+        from services.main.models import *
+        from services.main.validation import *
+        from services.main.utils import *
+        from services.main.dependencies import *
+        from services.main.main import *
+    else:
+        # Re-raise (likely a missing external dependency like sqlalchemy)
+        raise