feat: release v0.2.0 profiles, chat, freeze, and bots

Ship the product pass on the v0.1.3 schema with additive migrations, a replica migration lock, and bot accounts kept out of people lists.

backend/internal/db/migrations/0024_last_seen.sql

@@ -0,0 +1 @@
+ALTER TABLE users ADD COLUMN IF NOT EXISTS last_seen_at TIMESTAMPTZ;