feat: add game page frontend with grid, word list, timer, and dual input

Recreates base.html and main.html templates (lost during reset).
Adds game.html with setup UI (category picker, board size slider),
interactive grid table, word list sidebar, text input, click-to-select,
timer, and completion banner. Adds game.js for all frontend logic.
Extends theme.css with game grid and form control styles using the
indigo/coral palette.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

alembic/versions/71016fe57b9d_initial_tables.py

@@ -11,7 +11,6 @@ from typing import Sequence, Union
 from alembic import op
 import sqlalchemy as sa
 
-
 # revision identifiers, used by Alembic.
 revision: str = "71016fe57b9d"
 down_revision: Union[str, Sequence[str], None] = None