Fix double snowflake and add i18n to admin page

- Remove default text from i18n spans to prevent double snowflake on main page
- Add i18n support to admin page with language selector
- Make admin panel title translatable

This ensures the snowflake emoji only appears once as a clickable link,
and the translated app name appears separately without its own snowflake.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

public/index.html

@@ -53,7 +53,7 @@
         <header>
             <div class="header-content">
                 <div class="header-text">
-                    <h1><a href="/" style="text-decoration: none; color: inherit;">❄️</a> <span data-i18n="common.appName">Great Lakes Ice Report</span></h1>
+                    <h1><a href="/" style="text-decoration: none; color: inherit;">❄️</a> <span data-i18n="common.appName"></span></h1>
                     <p data-i18n="meta.subtitle">Community-reported ICEy road conditions and winter hazards (auto-expire after 48 hours)</p>
                 </div>
                 <div class="header-controls">