feat(engagement): localize limits and streaks

Use reported user timezones for daily response limits, expose couple streak state and reminders, and improve swipe and live-drawing synchronization with focused tests and documentation.

apps/api/drizzle/0013_daily_limit_local_reset.sql

@@ -0,0 +1,2 @@
+ALTER TABLE "profiles" ADD COLUMN IF NOT EXISTS "timezone" text;--> statement-breakpoint
+COMMENT ON COLUMN "profiles"."timezone" IS 'IANA zone reported by the client. NULL falls back to UTC when bucketing the daily response limit.';