Change events.occurred_at from TIMESTAMPTZ to DATE

Make date required, remove default. Simplifies date handling
throughout the controller.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

resources/migrations/20260308200000-events-occurred-at-date.down.sql

@@ -0,0 +1,5 @@
+ALTER TABLE deposits ALTER COLUMN occurred_at TYPE TIMESTAMPTZ USING occurred_at::timestamptz;
+--;;
+ALTER TABLE events ALTER COLUMN occurred_at SET DEFAULT NOW();
+--;;
+ALTER TABLE events ALTER COLUMN occurred_at TYPE TIMESTAMPTZ USING occurred_at::timestamptz;

resources/migrations/20260308200000-events-occurred-at-date.up.sql

@@ -0,0 +1,5 @@
+ALTER TABLE events ALTER COLUMN occurred_at TYPE DATE USING occurred_at::date;
+--;;
+ALTER TABLE events ALTER COLUMN occurred_at DROP DEFAULT;
+--;;
+ALTER TABLE deposits ALTER COLUMN occurred_at TYPE DATE USING occurred_at::date;