feat(highscore-server): store a crazy-mode flag per score

The game is getting a crazy mode that drops extra balls, and scores
reached with it should still enter the shared table but be visibly
labelled. The service therefore has to persist and return that label.

API:
- POST /api/highscores accepts an optional "crazy" boolean. Missing
  means false, so cached clients from before crazy mode keep working.
- GET responses include "crazy" on every entry. Older clients ignore
  unknown fields (serde default behaviour), so the new response shape is
  safe for them too.

Database:
- New databases get a `crazy INTEGER NOT NULL DEFAULT 0 CHECK (crazy IN
  (0, 1))` column.
- Existing databases are migrated on open: if pragma_table_info shows no
  `crazy` column, ALTER TABLE adds it with the same definition. SQLite
  fills existing rows with the default, so every historic score stays a
  normal score. No data is rewritten and the migration is idempotent.

Ordering and the top-ten pruning are unchanged; the flag is not part of
the ranking.

Test Plan:
- cargo test --manifest-path highscore-server/Cargo.toml
  - pre_crazy_mode_database_is_migrated_in_place: builds the old schema
    with a row, opens it, submits a crazy score, checks both rows come
    back with the right flag, and reopens the migrated file.
  - api_accepts_crazy_flag_and_defaults_it_for_old_clients: one request
    without the field, one with "crazy": true.
- Deploy: restart the service against the production database and check
  GET /api/highscores lists the old entries with "crazy": false.

tdkpin-rs/CHANGELOG.md

@@ -13,6 +13,9 @@ and this project adheres to
 - Crazy mode: Ctrl+Shift+0 drops ten extra balls onto the playfield. They bounce
   and score off walls, bumpers, and flippers, replace the main ball when it
   drains, and keep the game's scores off the online high-score table.
+- The high-score service stores a crazy-mode flag per entry; it adds the column
+  to existing databases on startup and treats submissions from older clients as
+  normal scores.
 
 ## [1.2.1] - 2026-09-01