Fix Quick-Buchen visibility: always show on negative buffer, hide when buf >= daily

Rules:
- buf < 0 (behind) → always visible to catch up
- buf >= daily (more than a day ahead) → hidden
- otherwise → visible only if today not yet reached daily goal

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

public/app.js

@@ -773,7 +773,7 @@ function buildCard(g){
 // ── Quick-Buchen ──────────────────────────────────────────────────────────────
 
 function buildQuickBook(){
-  var active=goals.filter(function(g){ var c=calc(g); return tOff(g)<g.days&&!c.ok&&c.buf<g.daily; });
+  var active=goals.filter(function(g){ var c=calc(g); return tOff(g)<g.days&&(c.buf<0||(c.tdone<g.daily&&c.buf<g.daily)); });
   if(!active.length) return null;
   var frag=document.createDocumentFragment();
   var lbl=document.createElement('div'); lbl.className='sec-lbl'; lbl.textContent=tr('qbLabel');