factor out resizing logic

Gemfile.lock

@@ -5,6 +5,14 @@ GIT
   specs:
     dtext_rb (1.11.0)
 
+GIT
+  remote: https://github.com/instructure/ruby-ffmpeg
+  revision: a3404b8fa275e2eb9549f074906461b0266a70ea
+  tag: v6.1.2
+  specs:
+    ffmpeg (6.1.2)
+      multi_json (~> 1.8)
+
 GIT
   remote: https://github.com/railsjazz/rails_live_reload
   revision: dcd3b73904594e2c5134c2f6e05954f3937a8d29
@@ -269,6 +277,7 @@ GEM
     mini_mime (1.1.5)
     minitest (5.25.4)
     msgpack (1.7.5)
+    multi_json (1.15.0)
     neighbor (0.5.1)
       activerecord (>= 7)
     net-imap (0.5.4)
@@ -582,6 +591,7 @@ DEPENDENCIES
   dtext_rb!
   factory_bot_rails
   faiss
+  ffmpeg!
   good_job (~> 4.6)
   htmlbeautifier
   http (~> 5.2)