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/templates/login.html

@@ -0,0 +1,16 @@
+{% extends "base.html" %}
+{% block title %}Login - ROSS Admin{% endblock %}
+{% block content %}
+<div class="card" style="max-width:360px;margin:60px auto;">
+  <h2 style="margin-top:0;">ROSS Admin Login</h2>
+  <form method="post">
+    <label>Username</label>
+    <input type="text" name="username" autofocus required>
+    <label>Passwort</label>
+    <input type="password" name="password" required>
+    <div style="margin-top:20px;">
+      <button type="submit">Login</button>
+    </div>
+  </form>
+</div>
+{% endblock %}