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/api/__init__.py

@@ -7,6 +7,7 @@ import logging
 from fastapi import APIRouter
 
 from app.api.azure import router as azure_router
+from app.api.database import router as database_router
 from app.api.diagnostic import router as diagnostic_router
 from app.api.dropbox import router as dropbox_router
 from app.api.duplicates import router as duplicates_router
@@ -52,3 +53,4 @@ router.include_router(saved_searches_router)
 router.include_router(similarity_router)
 router.include_router(duplicates_router)
 router.include_router(webhooks_router)
+router.include_router(database_router)