feat(users): add admin-granted verified badge for trusted contributors

- migration 0002: users.verified boolean, default false
- verified rides in the JWT (role + verified claims)
- POST /users/{id}/verify + /unverify, admin-only (403 otherwise)
- Issue now takes the whole user so trust claims travel in the token
- unit + integration + admin-flow tests

users/migrations/0002_user_verified.down.sql

@@ -0,0 +1,5 @@
+BEGIN;
+
+ALTER TABLE users DROP COLUMN IF EXISTS verified;
+
+COMMIT;

users/migrations/0002_user_verified.up.sql

@@ -0,0 +1,9 @@
+BEGIN;
+
+-- A "verified" account is a trusted contributor: the coordinator accepts its
+-- workers' results directly, without quorum cross-checking. Distinct from role
+-- (which governs what a user may do with their own jobs). Granted by an admin,
+-- never self-served; defaults to false, so a fresh account is untrusted.
+ALTER TABLE users ADD COLUMN verified boolean NOT NULL DEFAULT false;
+
+COMMIT;