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/package-lock.json

@@ -8,6 +8,9 @@
       "name": "frontend",
       "version": "0.0.0",
       "dependencies": {
+        "@fontsource/alegreya-sans": "^5.2.8",
+        "@fontsource/alegreya-sc": "^5.2.8",
+        "@fontsource/pirata-one": "^5.2.8",
         "svelte-spa-router": "^5.1.0"
       },
       "devDependencies": {
@@ -50,6 +53,33 @@
         "tslib": "^2.4.0"
       }
     },
+    "node_modules/@fontsource/alegreya-sans": {
+      "version": "5.2.8",
+      "resolved": "https://registry.npmjs.org/@fontsource/alegreya-sans/-/alegreya-sans-5.2.8.tgz",
+      "integrity": "sha512-kXUTR1S6dsWa7rBxaDJ3P05HodmYmxfY20aQtQ4SYVmrEYrWtaw5A1n+h+wcCF0nAMwf+CQ4M435dNuWD1YfMg==",
+      "license": "OFL-1.1",
+      "funding": {
+        "url": "https://github.com/sponsors/ayuhito"
+      }
+    },
+    "node_modules/@fontsource/alegreya-sc": {
+      "version": "5.2.8",
+      "resolved": "https://registry.npmjs.org/@fontsource/alegreya-sc/-/alegreya-sc-5.2.8.tgz",
+      "integrity": "sha512-28ZMhxJ/bx7f9S2oTTPeXvKchAu5VxPbEG95RI+EI9l3/1YyomEXzUqX0lCdCQb5fDXhdmVwHSD07P0BL4ueQA==",
+      "license": "OFL-1.1",
+      "funding": {
+        "url": "https://github.com/sponsors/ayuhito"
+      }
+    },
+    "node_modules/@fontsource/pirata-one": {
+      "version": "5.2.8",
+      "resolved": "https://registry.npmjs.org/@fontsource/pirata-one/-/pirata-one-5.2.8.tgz",
+      "integrity": "sha512-hl3Zqt6mgP+jstHnv2qYc2xQdYM1DSYrpSU9bpS1fYExoGFgJJNbXTPBQ9XivNk9RCKkibhou3iqoOZQOXM48w==",
+      "license": "OFL-1.1",
+      "funding": {
+        "url": "https://github.com/sponsors/ayuhito"
+      }
+    },
     "node_modules/@jridgewell/gen-mapping": {
       "version": "0.3.13",
       "resolved": "https://registry.npmjs.org/@jridgewell/gen-mapping/-/gen-mapping-0.3.13.tgz",