fix(migrations): renumber feed-view migration 006 → 010

The new v_feed-rewrite migration collided with the existing 006_user_pin_lockout
(versions must be unique). Verified against a fresh Postgres: all migrations
001–010 now apply cleanly on startup.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/migrations/010_feed_view_perf.up.sql

@@ -0,0 +1,26 @@
+-- H6: replace v_feed's double LEFT JOIN + COUNT(DISTINCT) (which materializes a
+-- likes×comments Cartesian per upload before de-duping) with correlated scalar
+-- subqueries. Each count now uses its own index (idx_like_upload /
+-- idx_comment_upload) and there is no GROUP BY. The output columns are
+-- unchanged, so every consumer keeps working.
+CREATE OR REPLACE VIEW v_feed AS
+SELECT
+    u.id,
+    u.event_id,
+    u.user_id,
+    usr.display_name             AS uploader_name,
+    usr.is_banned,
+    usr.uploads_hidden,
+    u.preview_path,
+    u.thumbnail_path,
+    u.mime_type,
+    u.caption,
+    u.created_at,
+    (SELECT COUNT(*) FROM "like" l
+       WHERE l.upload_id = u.id)                              AS like_count,
+    (SELECT COUNT(*) FROM comment c
+       WHERE c.upload_id = u.id AND c.deleted_at IS NULL)     AS comment_count
+FROM upload u
+JOIN "user" usr ON u.user_id = usr.id
+WHERE u.deleted_at IS NULL
+  AND usr.uploads_hidden = FALSE;