merge: integrate main restructuring into dev

- Resolve 57 merge conflicts from codebase restructure
- Port dev feature code to new directory structure:
  * Update import paths to use @/ aliases
  * Add backward-compatible API signatures (createInstance, startInstance, deleteInstance)
  * Add missing type exports (ProjectWithRepos, InstanceHealth, Branch, BranchesResponse)
  * Extend Session and GitRepository types for dev features
  * Extend TerminalComponent props for mobile terminal wrapper
  * Add missing icon names (bell, drag, undo)

Quality gates: tsc pass (0 errors), build pass, 127/131 tests pass
(4 pre-existing failures unrelated to merge)

apps/api/tests/integration/test_projects_api.py

@@ -1,5 +1,5 @@
 import uuid
-from datetime import UTC, datetime, timedelta
+from datetime import datetime, timedelta, timezone
 import asyncio
 
 import pytest
@@ -59,7 +59,7 @@ def _mint_token(user_id: str) -> str:
         subject=user_id,
         email="test@headquarter.local",
         name="Test User",
-        expires_at=datetime.now(UTC) + timedelta(minutes=15),
+        expires_at=datetime.now(timezone.utc) + timedelta(minutes=15),
     )