Feature: Forum-Beiträge von Freunden im Aktivitäts-Feed + Deep-Link

- friends.py: forum_threads im Activity-Feed (mit entry_id)
- Filter-Chip 'Forum' ergänzt
- Klick öffnet direkt den Forum-Thread via App.callModule('forum','openThread',id)

backend/routes/friends.py

@@ -277,6 +277,25 @@ async def get_activity(user=Depends(get_current_user)):
             LIMIT 15
         """, friend_ids).fetchall()
 
+        # Forum-Beiträge der Freunde (öffentliche Threads)
+        forum_rows = conn.execute(f"""
+            SELECT
+                'forum'          AS type,
+                ft.id            AS entry_id,
+                u.id             AS user_id,
+                u.name           AS user_name,
+                u.avatar_url,
+                NULL             AS dog_name,
+                NULL             AS dog_foto,
+                ft.titel         AS text,
+                ft.created_at
+            FROM forum_threads ft
+            JOIN users u ON u.id = ft.user_id
+            WHERE ft.user_id IN ({ph})
+            ORDER BY ft.created_at DESC
+            LIMIT 15
+        """, friend_ids).fetchall()
+
         # Neue Hunde (angelegt in den letzten 30 Tagen)
         new_dog_rows = conn.execute(f"""
             SELECT
@@ -300,6 +319,7 @@ async def get_activity(user=Depends(get_current_user)):
         "health":  "heart",
         "walk":    "paw-print",
         "new_dog": "dog",
+        "forum":   "push-pin",
     }
     _TEXT = {
         "health":  "Hat einen Gesundheitseintrag hinzugefügt",
@@ -307,7 +327,7 @@ async def get_activity(user=Depends(get_current_user)):
     }
 
     items = []
-    for row in [*diary_rows, *health_rows, *walk_rows, *new_dog_rows]:
+    for row in [*diary_rows, *health_rows, *walk_rows, *forum_rows, *new_dog_rows]:
         d = dict(row)
         t = d["type"]
         items.append({