auto-claude: subtask-1-3 - Add filtering logic and integrate components into blog page

- Created BlogList client component with search and category filtering
- Integrated SearchBar and CategoryFilter components
- Implemented case-insensitive search by title/excerpt/tags
- Added category filtering with AND logic for combined filters
- Updated pagination to work with filtered results
- Added search placeholder translations for de/en/sr
- Moved blog card and pagination logic to client component

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

src/messages/de.json

@@ -463,12 +463,15 @@
     },
     "ui": {
       "readMore": "Weiterlesen",
+      "search": {
+        "placeholder": "Beiträge durchsuchen..."
+      },
       "loading": {
         "posts": "Blogbeiträge werden geladen...",
         "post": "Blogbeitrag wird geladen..."
       },
       "errors": {
-        "posts": "Fehler beim Laden der Blogbeiträge",
+        "posts": "Keine Beiträge gefunden",
         "post": "Der gesuchte Blogbeitrag existiert nicht oder wurde verschoben."
       },
       "backToBlog": "Zurück zum Blog",