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/conftest.py

@@ -8,16 +8,14 @@ from unittest.mock import patch
 import pytest
 import pytest_asyncio
 from fastapi.testclient import TestClient
-from sqlalchemy import create_engine, text
 from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
-from sqlalchemy.orm import sessionmaker
 
 # Set test environment BEFORE importing app modules
 os.environ["APP_ENV"] = "testing"
 os.environ["SECRET_KEY"] = "test-secret-key-for-testing-only-do-not-use-in-production"
 os.environ["DATABASE_URL"] = "sqlite+aiosqlite:///:memory:"
 
-from src.config import Settings, build_database_url
+from src.config import Settings
 from src.models.base import Base
 from src.main import app
 from src.auth.dependencies import get_db_session