style: fix all ruff and eslint errors across codebase

Backend (ruff):
- Fix 106 errors: move imports to top of file (E402)
- Remove unused imports (F401)
- Add missing imports for undefined names (F821)
- Remove unused variables (F841)
- Fix test_models.py broken RefreshToken test
- Fix test_projects_api.py missing TestClient import

Frontend (eslint):
- Remove unused imports/variables across 10 files
- Fix explicit any types in client.ts and sessions.ts
- Clean up empty block statements in terminal.tsx

Quality gates: ruff (pass), eslint (pass), tsc --noEmit (pass),
pytest (98 passed, 4 pre-existing failures)

apps/api/tests/unit/test_config_profile_resolver.py

@@ -6,7 +6,6 @@ from src.models.config_profile import ConfigProfile, ConfigProfileInclude
 from src.services.config_profile_resolver import (
     ConfigProfileCycleError,
     ConfigProfileNotFoundError,
-    ResolvedProfile,
     check_include_cycle,
     resolve_profile,
     _merge_env_vars,
@@ -63,7 +62,6 @@ class TestMergeFunctions:
 
     def test_merge_mounts_basic(self) -> None:
         """Test basic mount merging."""
-        from src.services.config_profile_resolver import ResolvedMount
         result = _merge_mounts(
             {},
             [{"target": "/app", "mode": "rw", "files": {"a.txt": "content"}}],