fix: cleanup codebase and sync SPEC with actual permissions

Phase 1: Ruff lint fixes
- Remove unused imports across all files
- Remove unused variables (now_utc, tz, ctx)
- Fix f-string without placeholders
- Fix E402 import order with noqa comments

Phase 2: Remove confusing hard delete from storage
- Removed delete_bounty() from RoomStorage Protocol (never used by app)
- Removed delete_bounty() from JsonFileRoomStorage (was hard delete)
- Removed corresponding tests (hard delete was never used)

Phase 3: Sync SPEC.md with actual code behavior
- Updated overview: admins can add/edit/delete (not 'anyone' + 'creator')
- Updated command table: /add, /edit, /delete are admin only
- Updated error handling messages

Test results: 96 passed (2 hard delete tests removed)

tests/test_services.py

@@ -1,9 +1,8 @@
 """Tests for core/services.py — business logic services."""
 
 import pytest
-from unittest.mock import MagicMock
 
-from core.models import Bounty, RoomData, TrackingData, TrackedBounty
+from core.models import RoomData
 from core.services import BountyService, TrackingService
 from tests.test_ports import MockRoomStorage, MockTrackingStorage