feat: full article fetching with trafilatura + html2text cleanup

- Add trafilatura + html2text to dependencies
- Replace custom HTMLStripper with html2text for RSS feed content
- Fetch full article text via httpx + trafilatura after each new item is stored;
  falls back to RSS-provided content if fetch/extraction fails
- Raise CONTENT_MAX_CHARS from 2000 to 50000 (TEXT column, no migration needed)
- Re-embed items with full article content once enrichment completes
- Startup backfill enriches existing items with short content (<1000 chars)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/fabledassistant/services/embeddings.py

@@ -297,3 +297,59 @@ async def backfill_rss_item_embeddings() -> None:
         await asyncio.sleep(0.05)
 
     logger.info("RSS embedding backfill complete: %d/%d items embedded", success, len(items_to_embed))
+
+
+async def backfill_rss_article_content() -> None:
+    """Fetch full article text for RSS items that only have short feed-provided content.
+
+    An item is considered unenriched if its content is shorter than 1000 chars —
+    typical of feed summaries/teasers rather than full articles.
+    Runs at startup after the embedding backfill.
+    """
+    from fabledassistant.services.rss import _fetch_full_article, CONTENT_MAX_CHARS
+    from fabledassistant.models.rss_feed import RssFeed
+
+    SHORT_THRESHOLD = 1000
+
+    try:
+        async with async_session() as session:
+            feed_result = await session.execute(select(RssFeed.id, RssFeed.user_id))
+            feed_user_map = {fid: uid for fid, uid in feed_result.fetchall()}
+
+            item_result = await session.execute(
+                select(RssItem.id, RssItem.feed_id, RssItem.url, RssItem.title, RssItem.content)
+                .where(RssItem.url != "")
+            )
+            candidates = [
+                row for row in item_result.fetchall()
+                if len(row[4] or "") < SHORT_THRESHOLD
+            ]
+    except Exception:
+        logger.warning("Article content backfill: failed to query items", exc_info=True)
+        return
+
+    if not candidates:
+        logger.info("Article content backfill: no unenriched items found")
+        return
+
+    logger.info("Article content backfill: enriching %d items", len(candidates))
+    enriched = 0
+    for item_id, feed_id, url, title, _ in candidates:
+        user_id = feed_user_map.get(feed_id)
+        if user_id is None:
+            continue
+        full_text = await _fetch_full_article(url)
+        if full_text and len(full_text) > SHORT_THRESHOLD:
+            try:
+                async with async_session() as session:
+                    item = await session.get(RssItem, item_id)
+                    if item:
+                        item.content = full_text[:CONTENT_MAX_CHARS]
+                        await session.commit()
+                await upsert_rss_item_embedding(item_id, user_id, title or "", full_text[:CONTENT_MAX_CHARS])
+                enriched += 1
+            except Exception:
+                logger.debug("Failed to store enriched content for item %d", item_id, exc_info=True)
+        await asyncio.sleep(0.5)
+
+    logger.info("Article content backfill complete: %d/%d items enriched", enriched, len(candidates))