feat: add 'video' as a new value to content_type enum

- Updated backend migrations to include 'video' in the `content_type` enum.
- Synced migration metadata files to reflect the schema changes.

backend/.migrations/0007_melodic_synch.sql

@@ -0,0 +1 @@
+ALTER TYPE "public"."content_type" ADD VALUE 'video';

backend/.migrations/meta/_journal.json

@@ -50,6 +50,13 @@
       "when": 1768423315172,
       "tag": "0006_friendly_adam_warlock",
       "breakpoints": true
+    },
+    {
+      "idx": 7,
+      "version": "7",
+      "when": 1769605995410,
+      "tag": "0007_melodic_synch",
+      "breakpoints": true
     }
   ]
 }