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_cli.py

@@ -3,7 +3,6 @@
 import pytest
 from unittest.mock import patch, MagicMock
 from io import StringIO
-import sys
 
 from core.models import Bounty
 from core.ports import RoomStorage, TrackingStorage
@@ -237,7 +236,7 @@ class TestCLIValidation:
                 main()
                 mock_bounty_service.update_bounty.assert_called_once()
                 call_kwargs = mock_bounty_service.update_bounty.call_args
-                assert call_kwargs.kwargs.get("clear_link") == True
+                assert call_kwargs.kwargs.get("clear_link") is True
 
     def test_update_clear_due_flag(self):
         """Test update with --clear-due flag."""
@@ -255,7 +254,7 @@ class TestCLIValidation:
                 main()
                 mock_bounty_service.update_bounty.assert_called_once()
                 call_kwargs = mock_bounty_service.update_bounty.call_args
-                assert call_kwargs.kwargs.get("clear_due") == True
+                assert call_kwargs.kwargs.get("clear_due") is True
 
 
 class TestCLIOutput: