feat(database): add database configuration wizard and migration tool

Add a guided database configuration wizard and a data migration tool that
allows users to:
- Build database connection strings through a step-by-step UI
- Test database connections before applying
- Preview and execute data migrations from SQLite to PostgreSQL/MySQL
- Copy to clipboard for easy .env file updates

New files:
- app/utils/db_wizard.py — connection string builder, parser, and tester
- app/utils/db_migrate.py — table-by-table data migration utility
- app/api/database.py — REST API endpoints for wizard operations
- app/views/db_wizard.py — view route for the wizard page
- frontend/templates/db_wizard.html — multi-tab wizard UI
- tests/test_db_wizard.py — unit tests for db_wizard utilities
- tests/test_db_migrate.py — unit tests for db_migrate utilities
- tests/test_db_wizard_api.py — integration tests for API and views

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>

app/views/__init__.py

@@ -4,6 +4,7 @@ Aggregated view routers for the application.
 
 from fastapi import APIRouter
 
+from app.views.db_wizard import router as db_wizard_router
 from app.views.dropbox import router as dropbox_router
 from app.views.filemanager import router as filemanager_router
 
@@ -21,6 +22,7 @@ from app.views.wizard import router as wizard_router
 # Create a main router that includes all the view routers
 router = APIRouter()
 router.include_router(wizard_router)  # Wizard first (for /setup)
+router.include_router(db_wizard_router)  # Database wizard
 router.include_router(general_router)
 router.include_router(status_router)
 router.include_router(onedrive_router)