Envelope budget: Budget page, per-month assignments stored on a Budget tab, rollover and ready-to-assign

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

app_page.html

@@ -28,7 +28,7 @@ th{font-size:12px;color:var(--mute);font-weight:600}td.num{text-align:right;font
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-  <div class="row"><h1 style="margin:0">Statement Loader</h1><div class="spacer"></div><a href="/dashboard" style="color:var(--accent);font-weight:600;text-decoration:none">Dashboard →</a></div>
+  <div class="row"><h1 style="margin:0">Statement Loader</h1><div class="spacer"></div><a href="/budget" style="color:var(--accent);font-weight:600;text-decoration:none;margin-right:14px">Budget</a><a href="/dashboard" style="color:var(--accent);font-weight:600;text-decoration:none">Dashboard →</a></div>
   <div class="sub">Runs only on this Mac. Drop in statements, check what’s covered, then add the new transactions to <b>Bills_Tracker.xlsx</b>. A backup is saved first, every time.</div>
 
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