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>

webadmin/requirements.txt

@@ -0,0 +1,3 @@
+Flask==3.0.3
+PyMySQL==1.1.1
+gunicorn==22.0.0