fix: no user ever had a username, so people search found nobody

Root cause of "still cannot find users": username was optional in
better-auth's schema and no signup form or settings page ever set it,
but search/profile/follow all key on username, not user id. Every
account now gets a unique one auto-generated (from name/email) in the
user.create.before hook — covers email/password and OAuth signups.
Added a one-off db:backfill-usernames script for accounts created
before this fix and ran it against the current database.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

CHANGELOG.md

@@ -2,6 +2,11 @@
 
 All notable changes to Epicure are documented here. This file is mirrored in-app at `/changelog` (and in the admin dashboard) via `apps/web/lib/changelog.ts` — update both together.
 
+## 0.13.1 — 2026-07-13 17:25
+
+### Fixed
+- People search never found anyone, for anyone — there was no signup or settings flow that ever set a username, and search (along with profiles and follow) requires one. Every account now gets one automatically on signup; existing accounts were backfilled.
+
 ## 0.13.0 — 2026-07-13 15:37
 
 ### Added