Feat: Move from Pages to a Worker and serve popular images as static files

Static assets don't count toward the free plan's 100,000 requests a day, so a
daily GitHub Action promotes the most viewed images (by Cloudflare analytics)
from R2 into public/ before deploying, and reports to ntfy. Zone rules fold
the site and ?i= into the path, since static files ignore query strings.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

public/assets/logo.svg

@@ -0,0 +1,12 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 64 64" fill="none" stroke-linecap="round" stroke-linejoin="round">
+  <style>
+    .f{stroke:#1a1a1a}.a{stroke:#0070f3}
+    @media (prefers-color-scheme:dark){.f{stroke:#f5f5f5}}
+  </style>
+  <!-- frame -->
+  <rect class="f" x="7" y="7" width="50" height="50" rx="13" stroke-width="4.5"/>
+  <!-- the URL "/" rising into a peak -->
+  <path class="f" d="M19 57 29 32l10 14 5-7 13 5" stroke-width="4.5"/>
+  <!-- a link as the sun -->
+  <path class="a" d="M-2-4h-3a4 4 0 0 0 0 8h3M2-4h3a4 4 0 0 1 0 8H2M-4 0h8" stroke-width="2.5" transform="translate(42 22) rotate(-45)"/>
+</svg>

public/assets/rate-limit.js

@@ -0,0 +1,6 @@
+// New searches (cache misses) allowed per IP per day, reset at 00:00 UTC. Cache hits never count.
+// Safe to edit by hand. Imported by the worker and by the homepage (as a static file, so no Functions quota).
+// The burst limit (~20 req/10s) is a Cloudflare WAF rule, not set here.
+export const DAILY_LIMIT = 10;
+export const FREE_DAILY_LIMIT = 100;
+export const AI_DAILY_LIMIT = 100;