logo: gradient square back, dog on top; footer wording

brand-dot is back to the blue→yellow gradient rounded square, and the
didi image sits centered inside it (span wrapper, flex-centered, 88%
inner size). The dog's transparent background lets the gradient peek
through around him.

Footer: "Programmiert für Annika ♥" → "Mit ♥ programmiert für Annika".

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

web/templates/_layout.html

@@ -7,7 +7,7 @@
 <header class="border-b border-soft bg-white/70 backdrop-blur sticky top-0 z-10">
     <div class="max-w-6xl mx-auto px-6 py-3 flex items-center justify-between">
         <div class="flex items-center gap-3">
-            <img src="/static/didi.webp" alt="" class="brand-dot">
+            <span class="brand-dot"><img src="/static/didi.webp" alt=""></span>
             <h1 class="text-xl font-semibold">wohnungsdidi</h1>
         </div>
         <div class="flex items-center gap-4 text-sm">
@@ -30,6 +30,6 @@
     {% block content %}{% endblock %}
 </main>
 <footer class="text-center text-xs text-slate-500 py-6">
-    Programmiert für Annika ♥
+    Mit ♥ programmiert für Annika
 </footer>
 {% endblock %}