style: apply ruff format across backend + scripts (line-length 100)

Mechanical, whole-tree `ruff format` pass — no behaviour change. Recorded in
.git-blame-ignore-revs (next commit) so git blame skips it.

backend/app/sync/explore.py

@@ -7,6 +7,7 @@ stay private to users who explored (or subscribe to) the channel — the feed qu
 — so one user's curiosity never floods everyone's catalog. Subscribing is the "keep" signal;
 otherwise the cleanup job hard-deletes the channel and its untouched ephemeral videos after a
 grace period (mirrors the maintenance job's grace-then-delete safety)."""
+
 import logging
 from datetime import timedelta
 
@@ -35,11 +36,7 @@ def _enrich_new(db: Session, yt: YouTubeClient, video_ids: list[str]) -> int:
     if not video_ids:
         return 0
     videos = (
-        db.execute(
-            select(Video).where(
-                Video.id.in_(video_ids), Video.enriched_at.is_(None)
-            )
-        )
+        db.execute(select(Video).where(Video.id.in_(video_ids), Video.enriched_at.is_(None)))
         .scalars()
         .all()
     )
@@ -101,17 +98,11 @@ def purge_unkept_explored(db: Session) -> dict:
     ).rowcount
     db.commit()
 
-    sub_exists = (
-        select(Subscription.id).where(Subscription.channel_id == Channel.id).exists()
-    )
-    exp_exists = (
-        select(ExploredChannel.id).where(ExploredChannel.channel_id == Channel.id).exists()
-    )
+    sub_exists = select(Subscription.id).where(Subscription.channel_id == Channel.id).exists()
+    exp_exists = select(ExploredChannel.id).where(ExploredChannel.channel_id == Channel.id).exists()
     orphan_ids = (
         db.execute(
-            select(Channel.id).where(
-                Channel.from_explore.is_(True), ~sub_exists, ~exp_exists
-            )
+            select(Channel.id).where(Channel.from_explore.is_(True), ~sub_exists, ~exp_exists)
         )
         .scalars()
         .all()
@@ -158,9 +149,7 @@ def purge_unkept_search(db: Session, grace_days: int | None = None) -> dict:
     cutoff = _now() - timedelta(days=grace)
     state_exists = select(VideoState.id).where(VideoState.video_id == Video.id).exists()
     pl_exists = select(PlaylistItem.id).where(PlaylistItem.video_id == Video.id).exists()
-    sub_exists = (
-        select(Subscription.id).where(Subscription.channel_id == Video.channel_id).exists()
-    )
+    sub_exists = select(Subscription.id).where(Subscription.channel_id == Video.channel_id).exists()
     deleted = db.execute(
         delete(Video).where(
             Video.via_search.is_(True),