Backfill blacklisted posts from next API pages

When blacklist filtering reduces results below page size, fetches
additional pages to fill the gap. Filtered posts from backfill
pages also go through the blacklist. Caps at 5 extra pages.

booru_viewer/gui/app.py

@@ -616,11 +616,33 @@ class BooruApp(QMainWindow):
         page = self._current_page
         limit = self._db.get_setting_int("page_size") or 40
 
+        # Gather blacklist filters once on the main thread
+        bl_tags = set()
+        if self._db.get_setting_bool("blacklist_enabled"):
+            bl_tags = set(self._db.get_blacklisted_tags())
+        bl_posts = self._db.get_blacklisted_posts()
+
+        def _filter(posts):
+            if bl_tags:
+                posts = [p for p in posts if not bl_tags.intersection(p.tag_list)]
+            if bl_posts:
+                posts = [p for p in posts if p.file_url not in bl_posts]
+            return posts
+
         async def _search():
             client = self._make_client()
             try:
-                posts = await client.search(tags=search_tags, page=page, limit=limit)
-                self._signals.search_done.emit(posts)
+                collected = []
+                current_page = page
+                max_pages = 5  # safety cap to avoid infinite fetching
+                for _ in range(max_pages):
+                    batch = await client.search(tags=search_tags, page=current_page, limit=limit)
+                    filtered = _filter(batch)
+                    collected.extend(filtered)
+                    if len(collected) >= limit or len(batch) < limit:
+                        break
+                    current_page += 1
+                self._signals.search_done.emit(collected[:limit])
             except Exception as e:
                 self._signals.search_error.emit(str(e))
             finally:
@@ -629,15 +651,6 @@ class BooruApp(QMainWindow):
         self._run_async(_search)
 
     def _on_search_done(self, posts: list) -> None:
-        # Client-side blacklist filtering
-        if self._db.get_setting_bool("blacklist_enabled"):
-            bl_tags = set(self._db.get_blacklisted_tags())
-            if bl_tags:
-                posts = [p for p in posts if not bl_tags.intersection(p.tag_list)]
-        # Filter blacklisted posts by URL
-        bl_posts = self._db.get_blacklisted_posts()
-        if bl_posts:
-            posts = [p for p in posts if p.file_url not in bl_posts]
         self._posts = posts
         self._status.showMessage(f"{len(posts)} results")
         thumbs = self._grid.set_posts(len(posts))