feat:video player, like button, and media fallbacks

Add VideoPlayer and LikeButton components with optimistic UI and /server
endpoints for likes. Update media processor to emit WebP and JPEG
fallbacks, store fallback URLs in the DB (migration + snapshot), add
video placeholder asset, and relax CSP media-src for R2.

drizzle/0004_large_doctor_strange.sql

@@ -0,0 +1,2 @@
+ALTER TABLE "find_media" ADD COLUMN "fallback_url" text;--> statement-breakpoint
+ALTER TABLE "find_media" ADD COLUMN "fallback_thumbnail_url" text;