added gifs scan at start

deploy/migrations/20260807140000_gif_catalog_seed_filename.down.sql

@@ -0,0 +1,2 @@
+DROP INDEX IF EXISTS public.gif_catalog_source_filename_uniq;
+ALTER TABLE public.gif_catalog DROP COLUMN IF EXISTS source_filename;

deploy/migrations/20260807140000_gif_catalog_seed_filename.up.sql

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+-- Tracks which gif_catalog entries came from a filesystem seed drop
+-- (data/gifs/, see files.Service.SeedGifs) vs. an admin-panel upload, so a
+-- restart can tell "already imported this file" from "brand new file" without
+-- re-transcoding every GIF on every startup. Empty for panel-created entries.
+ALTER TABLE public.gif_catalog ADD COLUMN source_filename text DEFAULT ''::text NOT NULL;
+
+-- Only seed-imported rows need uniqueness here: two panel uploads may
+-- legitimately share nothing to compare, but two seed imports of the same
+-- filename must collapse to one row on every restart.
+CREATE UNIQUE INDEX gif_catalog_source_filename_uniq
+    ON public.gif_catalog (source_filename)
+    WHERE source_filename <> '';