fix(embeddings): remove stale CONTENT_MAX_CHARS import from rss.py

CONTENT_MAX_CHARS was removed from rss.py when the article content cap
was lifted. backfill_rss_article_content still referenced it, causing an
ImportError on startup.

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

src/fabledassistant/services/embeddings.py

@@ -310,7 +310,7 @@ async def backfill_rss_article_content() -> None:
     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.services.rss import _fetch_full_article
     from fabledassistant.models.rss_feed import RssFeed
 
     SHORT_THRESHOLD = 1000
@@ -348,9 +348,9 @@ async def backfill_rss_article_content() -> None:
                 async with async_session() as session:
                     item = await session.get(RssItem, item_id)
                     if item:
-                        item.content = full_text[:CONTENT_MAX_CHARS]
+                        item.content = full_text
                         await session.commit()
-                await upsert_rss_item_embedding(item_id, user_id, title or "", full_text[:CONTENT_MAX_CHARS])
+                await upsert_rss_item_embedding(item_id, user_id, title or "", full_text)
                 enriched += 1
             except Exception:
                 logger.debug("Failed to store enriched content for item %d", item_id, exc_info=True)