Type safety and cleanup refactor

[ATGillespie25]

Summary

No-behavior-change refactor improving type safety, removing dead code, and reducing duplication across server infrastructure.

Type safety:

• GameStatus(str, Enum) replacing raw status strings — assignment sites updated, comparisons still work via str inheritance
• Suit/SpecialRank IntEnums replacing bare int constants, with backward-compatible aliases
• DiceSet.kept/locked changed from list[int] to set[int] — matches the membership-only semantics, deduplication is automatic
• RefreshTokenRecord dataclass replacing untyped sqlite3.Row access
• Database._get_conn() raises RuntimeError instead of letting AttributeError propagate on null connection
• GameProtocol(Protocol) documenting the 17-mixin contract on Game
• is_bot property added to User ABC (default False), removing defensive getattr/hasattr checks
• Table._manager/_server/_db typed under TYPE_CHECKING instead of Any
• validate_actions() checks handler strings resolve at game start, logs warnings for typos
• Username reverse index on WebSocketServer for O(1) send_to_user/get_client_by_username

Cleanup:

• Deleted dead files: main.py (divergent unused entry point), protocol.py (unused packet types), ui/menu.py (unused Menu class)
• Removed dead tomli fallback imports (project requires Python 3.13+)
• Removed empty TYPE_CHECKING guards, fixed stale tick-rate comments
• Extracted _iter_approved_users, _build_action_menu_items, _show_user_list_menu helpers
• Consolidated config loading through existing load_full_config()
• Simplified VirtualBotConfig construction with dataclasses.fields() introspection

Tests (60 new):

• test_cards.py, test_dice.py, test_teams.py, test_round_timer.py, test_game_communication_mixin.py
• Existing dice-related tests updated for set-typed fields

Test plan

• All 341 affected tests pass
• CLI simulate pig --bots 3 completes
• CLI simulate threes --bots 3 --test-serialization completes (exercises DiceSet set serialization)
• Reviewed by code-reviewer and silent-failure-hunter agents; critical findings (username index race condition, threes list-to-set assignment, config error handling) fixed before commit

[zarvox32]

Tested locally and it's in good shape — 149 tests in the new/updated test files pass, 299 broader tests pass, and CLI simulations complete for pig, threes, yahtzee, twentyone, and milebymile (all with --test-serialization).

A few minor follow-up suggestions, none blocking:

1. Post-rebase sweep for GameStatus (most important)
Since this branched from 0d954fc, main has since merged #215, #225, #231, which touched server/games/milebymile/game.py and server/games/twentyone/game.py and added new self.status = "playing" / "finished" assignments that didn't get converted to the enum. GitHub marks the branch mergeable and the raw-string comparisons still work due to str inheritance, but a quick follow-up pass after rebase would keep the codebase consistent with the PR's stated goal.

2. status field type drift
status: str = GameStatus.WAITING declares str but assigns an enum. After a mashumaro round-trip the field becomes a plain string, so isinstance(status, GameStatus) or type(status) is str checks would behave differently before vs. after save/load. Equality comparisons are unaffected and nothing in the tree relies on this today — just a trap worth flagging for future readers.

3. _get_conn() now raises RuntimeError
Behaviour change from AttributeError to RuntimeError is cleaner, but worth calling out in case anyone had catch blocks tuned to the old type. Grepped — nothing relies on it.

4. validate_actions() logs warnings only
Handler-string typos now surface as WARN on the playpalace.actions logger instead of blowing up at runtime. Good for development ergonomics; worth making sure production logging is configured so a typo doesn't go silent until something explicitly triggers it.