feat(ugc): staff reprocessing of a property goes to the front of the queue

/reprocessproperty and the dashboard's Reprocess all models mark the
property's models as priority (ugc.priority, migrations mysql 94 and sqlite
77). The UGC server takes priority models first, polls them even when its
queue is full, and puts them at its front, as it does cars and rockets. The
flag clears once a model is made.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

migrations/dlu/sqlite/77_ugc_priority.sql

@@ -0,0 +1,2 @@
+/* ugc.priority: models staff asked to be made again. See the MySQL migration. */
+ALTER TABLE ugc ADD COLUMN priority INTEGER NOT NULL DEFAULT 0;