feat: themed 404 and 500 pages

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

fabledscryer/app.py

@@ -2,7 +2,7 @@
 from __future__ import annotations
 import asyncio
 from pathlib import Path
-from quart import Quart
+from quart import Quart, render_template
 from .config import load_bootstrap
 from .database import init_db
 
@@ -161,6 +161,15 @@ def create_app(
     async def health():
         return {"status": "ok"}
 
+    # ── 12. Error handlers ─────────────────────────────────────────────────────
+    @app.errorhandler(404)
+    async def not_found(_):
+        return await render_template("errors/404.html"), 404
+
+    @app.errorhandler(500)
+    async def server_error(_):
+        return await render_template("errors/500.html"), 500
+
     # ── 11. Startup hook ───────────────────────────────────────────────────────
     @app.before_serving
     async def startup():

fabledscryer/templates/errors/404.html

@@ -0,0 +1,10 @@
+{% extends "base.html" %}
+{% block title %}Not Found — Fabled Scryer{% endblock %}
+{% block content %}
+<div style="text-align:center; padding: 4rem 2rem; font-family: var(--font-serif);">
+  <h1 style="color: var(--gold); font-size: 2.5rem; margin-bottom: 0.5rem;">404</h1>
+  <p style="color: var(--text); font-size: 1.2rem; margin-bottom: 0.25rem;">No such seat at this table.</p>
+  <p style="color: var(--text-dim); margin-bottom: 1.5rem;">The page you sought is not among us.</p>
+  <a href="/" class="btn">Return to the hall</a>
+</div>
+{% endblock %}

fabledscryer/templates/errors/500.html

@@ -0,0 +1,10 @@
+{% extends "base.html" %}
+{% block title %}Error — Fabled Scryer{% endblock %}
+{% block content %}
+<div style="text-align:center; padding: 4rem 2rem; font-family: var(--font-serif);">
+  <h1 style="color: var(--red); font-size: 2.5rem; margin-bottom: 0.5rem;">500</h1>
+  <p style="color: var(--text); font-size: 1.2rem; margin-bottom: 0.25rem;">The watch has faltered.</p>
+  <p style="color: var(--text-dim); margin-bottom: 1.5rem;">An unexpected error occurred. The cause has been logged.</p>
+  <a href="/" class="btn">Return to the hall</a>
+</div>
+{% endblock %}