Add web admin panel for accounts/characters (login, GM rights, live stats)

New "webadmin" service (Flask + PyMySQL, port 8081) backing a small
server-rendered admin UI:
- Login gated on an existing game account: only accounts with
  accesslevel >= ADMIN_MIN_ACCESSLEVEL (default 900) get in. Password
  is MD5-hashed before comparison since the game client hashes it
  client-side before it ever hits the wire -- accounts.password is
  always an MD5 hex digest, confirmed against existing DB rows.
- Accounts: list/search, create, edit accesslevel/active/password.
- Characters: list/search, create (mirrors the real char-creation
  INSERT in Src/Char Server/charpackets.cpp -- only account_name,
  char_name, face, hairStyle, sex are set, everything else relies on
  the table's own defaults), edit core stats (level, zuly, attributes,
  hp/mp, stat/skill points) and isgm/isdev flags directly.

All queries are parameterized (no string-formatted SQL). No CSRF
protection or rate limiting yet -- acceptable for a small
already-behind-a-high-accesslevel-gate private server, worth
revisiting before ever exposing this port publicly.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

docker-compose.yml

@@ -89,6 +89,24 @@ services:
     volumes:
       - "./webtools:/usr/share/nginx/html:ro"
 
+  webadmin:
+    build:
+      context: ./webadmin
+    restart: unless-stopped
+    environment:
+      DB_HOST: db
+      DB_PORT: "3306"
+      DB_USER: ${DB_USER:-rose}
+      DB_PASSWORD: ${DB_PASSWORD:-change_me}
+      DB_NAME: ${DB_NAME:-ktrose}
+      ADMIN_SECRET_KEY: ${ADMIN_SECRET_KEY:-change-me-too}
+      ADMIN_MIN_ACCESSLEVEL: ${ADMIN_MIN_ACCESSLEVEL:-900}
+    ports:
+      - "8081:8080"
+    depends_on:
+      db:
+        condition: service_healthy
+
 volumes:
   db-data:
   logs: