feat: add scoreboard with player names, per-category leaderboards, and themed tables

Add player_name column to games (migration included), with regex-based
validation and anti-abuse sanitization. New /scoreboard page shows recent
games from localStorage, popular categories with play counts, and top-10
per-category leaderboards sorted by completion time. Also includes
two-click reverse word matching, base URL prefix support for reverse-proxy
hosting, BasePageHandler refactoring, themed table CSS for all 5 themes,
and comprehensive test coverage for player names and scoreboard API.

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

README.md

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+# ai_demo_backend
+
+A backend HTTP server that powers a word search puzzle game playable in a web browser. Built with Python and Tornado.
+
+## What is Word Search?
+
+Word search is a puzzle where a grid of letters contains hidden words placed horizontally, vertically, or diagonally. Players scan the grid to find and select each hidden word from a provided list.
+
+This backend serves the game logic — generating puzzles, validating found words, and managing game state — over HTTP for a browser-based frontend.
+
+## Installation
+
+Requires Python 3.13+ and [uv](https://docs.astral.sh/uv/).
+
+```sh
+uv sync
+```
+
+This installs all runtime and dev dependencies into a local `.venv`.
+
+## Database Setup
+
+Apply migrations and seed the database with word categories (animals, colors, food):
+
+```sh
+uv run alembic upgrade head
+uv run python seed.py
+```
+
+This creates a local `wordsearch.db` SQLite file. The seed script is idempotent — running it again skips existing categories.
+
+## Development
+
+Format code:
+
+```sh
+uv run black .
+```
+
+Lint:
+
+```sh
+uv run flake8
+```
+
+## Testing
+
+Run all tests:
+
+```sh
+uv run pytest
+```
+
+Run only unit tests:
+
+```sh
+uv run pytest tests/unit
+```
+
+Run only e2e tests:
+
+```sh
+uv run pytest tests/e2e
+```
+
+## Documentation
+
+Build the API documentation:
+
+```sh
+uv run sphinx-build -b html docs/source docs/build/html
+```
+
+Then open `docs/build/html/index.html` in a browser.
+
+## See Also
+ * Mathew Guest
+ * Co-Authored with Claude