rename: kafka → samsa

Full project rename from kafka to samsa (after Gregor Samsa, who
woke one morning from uneasy dreams to find himself transformed).

- Module: github.com/metamorphosis-dev/kafka → samsa
- Binary: cmd/kafka/ → cmd/samsa/
- CSS: kafka.css → samsa.css
- UI: all 'kafka' product names, titles, localStorage keys → samsa
- localStorage keys: kafka-theme → samsa-theme, kafka-engines → samsa-engines
- OpenSearch: ShortName, LongName, description, URLs updated
- AGPL headers: 'kafka' → 'samsa'
- Docs, configs, examples updated
- Cache key prefix: kafka: → samsa:

internal/views/templates/preferences.html

@@ -102,7 +102,7 @@
   var themeButtons = document.querySelectorAll('.theme-btn');
 
   // Load saved theme
-  var savedTheme = localStorage.getItem('kafka-theme') || 'light';
+  var savedTheme = localStorage.getItem('samsa-theme') || 'light';
   themeInput.value = savedTheme;
   document.querySelectorAll('.theme-btn').forEach(function(btn) {
     btn.classList.toggle('active', btn.dataset.theme === savedTheme);
@@ -116,12 +116,12 @@
       themeButtons.forEach(function(b) { b.classList.remove('active'); });
       btn.classList.add('active');
       document.documentElement.setAttribute('data-theme', theme);
-      localStorage.setItem('kafka-theme', theme);
+      localStorage.setItem('samsa-theme', theme);
     });
   });
 
   // Load saved engine preferences
-  var savedEngines = JSON.parse(localStorage.getItem('kafka-engines') || 'null');
+  var savedEngines = JSON.parse(localStorage.getItem('samsa-engines') || 'null');
   if (savedEngines) {
     savedEngines.forEach(function(engine) {
       var checkbox = document.querySelector('input[name="engine"][value="' + engine.id + '"]');
@@ -135,7 +135,7 @@
     document.querySelectorAll('input[name="engine"]').forEach(function(cb) {
       engines.push({ id: cb.value, enabled: cb.checked });
     });
-    localStorage.setItem('kafka-engines', JSON.stringify(engines));
+    localStorage.setItem('samsa-engines', JSON.stringify(engines));
   });
 })();
 </script>