refactor: route remaining fetch() calls through data/ modules

bookshelves.js used direct Gitea API fetch() for commit banners and
PR bookshelves. weather.js used direct Open-Meteo fetch() for weather.
Route both through their respective data/ modules (data/gitea.js and
data/weather.js). Add fetchMergedPRs() to data/gitea.js.

The one remaining fetch() in weather.js (runPortalHealthChecks) is a
no-cors connectivity probe, not data collection — accepted exception.

Fixes #421

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

modules/data/gitea.js

@@ -139,4 +139,25 @@ export async function refreshAgentData() {
   }
 }
 
+export async function fetchMergedPRs(limit = 20) {
+  try {
+    const res = await fetch(
+      `${GITEA_BASE}/repos/Timmy_Foundation/the-nexus/pulls?state=closed&limit=${limit}`,
+      { headers: { 'Authorization': `token ${GITEA_TOKEN}` } }
+    );
+    if (!res.ok) return [];
+    const data = await res.json();
+    return data
+      .filter(p => p.merged)
+      .map(p => ({
+        prNum: p.number,
+        title: p.title
+          .replace(/^\[[\w\s]+\]\s*/i, '')
+          .replace(/\s*\(#\d+\)\s*$/, ''),
+      }));
+  } catch {
+    return [];
+  }
+}
+
 export { GITEA_BASE, GITEA_TOKEN, GITEA_REPOS, AGENT_NAMES, CACHE_MS as AGENT_STATUS_CACHE_MS };