Re-theme the app: token-based CSS and a full face lift

CSS refactor: every color, font, radius, and shadow is now defined once
in theme.css; all other styles derive translucent variants with
color-mix(), so re-theming means editing one file. Removed the
duplicate core.css/style.css import chains, dead styles, and the
Bootstrap/Tailwind orphan classes that were silently unstyled
(the main reason the splash page looked broken).

New "Lantern & Brine" look: brass and parchment on a lantern-lit
ink-navy night, Pirata One wordmark with Alegreya SC/Sans body fonts
(self-hosted via fontsource — they were previously referenced but
never loaded), parchment-faced playing cards, and a rebuilt splash
page. Inline color styles in components were replaced with semantic
classes (prompt-box, notice-banner, status chips, etc.), the rulebook's
embedded palette was updated to match, and the leftover Vite favicon
and "frontend" page title were replaced.

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

frontend/src/pages/Join.svelte

@@ -26,11 +26,12 @@
 </script>
 
 <div class="welcome-container">
-    <div class="header">
-        <h1>Join Crew</h1>
-    </div>
+    <header class="welcome-hero">
+        <p class="hero-overline">Rats with Gats</p>
+        <h1 class="wordmark">Join the Crew</h1>
+    </header>
 
-    <div class="card creation-card">
+    <div class="glass-panel creation-card">
         <h2>Enter your name</h2>
         <p class="info-text" style="margin-bottom: 1rem;">
             This is <strong>your</strong> name as a player, not your Pi-Rat's. Your Pi-Rat will be known
@@ -44,7 +45,7 @@
                     id="playerName" 
                     bind:value={playerName} 
                     required 
-                    class="form-control input-large"
+                    class="input-field input-large"
                     autocomplete="off"
                     autofocus
                 />
@@ -54,7 +55,7 @@
                 <div class="alert alert-danger">{error}</div>
             {/if}
 
-            <button type="submit" class="btn btn-primary btn-large btn-block mt-4" disabled={joining}>
+            <button type="submit" class="btn btn-primary btn-large btn-full mt-4" disabled={joining}>
                 {joining ? 'Joining...' : 'Join Game'}
             </button>
         </form>