feat: add delete repository functionality

[Selene29]

Summary

• Add delete_repository and list_page_ids CRUD helpers, plus delete_many for FTS cleanup
• Add DELETE /api/repos/{repo_id} endpoint that cascades through DB rows and FTS index
• Add repowise delete CLI command with interactive repo selection and --force flag
• Add delete button to the dashboard UI (hover icon) with confirmation dialog
• Add delete button to repo settings page under a Danger Zone card — fixes single-repo setups where the dashboard auto-redirects past the list

Test plan

• Unit tests for CRUD delete_repository and list_page_ids
• API endpoint tests for DELETE /api/repos/{repo_id} (success + 404)
• Manual: run repowise delete CLI and verify repo is removed
• Manual: click delete button in dashboard, confirm dialog, verify repo disappears
• Manual: navigate to /repos/{id}/settings, verify Danger Zone section with Delete Repository button

[RaghavChamadiya]

Full-stack delete is well done. CRUD, API, CLI, and both UI surfaces (dashboard and Danger Zone) are all covered. The FTS cleanup before CASCADE delete is the right order.

Two issues I found in the code:

1. CLI argument parsing bug (delete_cmd.py): There are two positional optional arguments, repo_id and path. Click assigns positional args left-to-right, so repowise delete /path/to/repo would assign the path string to repo_id, then fail when trying to look it up as a UUID. The path argument is effectively unreachable. Suggest making path an option (--path) instead of a positional argument.

2. FTS skip when None (repos.py): In delete_repo, FTS cleanup is skipped when fts is None. If FTS was not initialized on a cold start, old FTS rows would linger. Is this a real scenario? If FTS is always initialized before any delete could happen, a comment explaining that would help future readers.

Logic and tests otherwise look solid. Fix the CLI argument issue and this is ready to merge.