Model permissions as (app, role) and name passkeys from their AAGUID

Two changes to the admin module, both made now because it is not deployed yet
and neither is free later.

Permissions were "an app", with a `role` column reserved for a future
fine-grained model. Reviewing whether that reservation was enough found three
problems:

- Every row was written with role = 'admin', hardcoded, and the column
  defaulted to it. On a `tickets` row that reads as "tickets administrator"
  when it only ever meant "has access", and once real roles existed there
  would have been no way to tell an old plain grant from a deliberate one.
- The role never left the database. /admin/me, the user list, the user detail
  and both write endpoints all spoke apps: AppName[]. Adding roles would have
  been a breaking change to /admin/me - and after the cutover that endpoint
  has two more consumers, turning a local edit into a coordinated deploy of
  three apps.
- The key (user_id, app) allowed one role per app, i.e. a tier rather than a
  set of capabilities. Choosing later means an ALTER on a live table.

So: the key is now (user_id, app, role), the role is `access`, and APP_ROLES
in admin.schema.ts is the contract - a role not listed there is rejected with
400 rather than written. permissions: [{app, role}] is on the wire alongside
the derived apps: AppName[], which is kept because the three frontends only
ever ask "may I show this app?". Both write endpoints accept either shape, and
the invitation column (now `permissions`) is parsed leniently: invitations live
seven days, so a deploy that changes the shape has in-flight rows in the old
one. requireAppAccess(app, role?) takes an optional role; nothing passes one
yet.

countActiveAdminsForUpdate now counts DISTINCT users rather than rows. With
several roles per app, counting rows would make a single admin holding two
roles look like two admins and defeat the last-admin guard at exactly the
moment it matters.

Separately, passkey registration now fills `name` from the authenticator's
AAGUID via registration.afterVerification and better-auth's own
getAuthenticatorName, yielding "1Password", "iCloud Keychain", "Windows Hello".
Without it the column stayed NULL and the account page could only label every
passkey "Passkey" - useless when someone has to remove the one on the device
they just lost. A client-supplied name still wins; an unknown AAGUID still
leaves it blank.

148 unit tests (up from 131, including the new admin.schema.test.ts) and 41
integration tests pass. The integration suite applies sql/admin/001_init.sql,
so the new key is exercised rather than trusted.

No production migration is needed - the module is not deployed. An existing dev
database needs three statements: set role = 'access', drop and re-add the
primary key, rename invitations.apps to permissions.

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

sql/admin/001_init.sql

@@ -114,15 +114,21 @@ CREATE TABLE IF NOT EXISTS `rateLimit` (
 -- ---------------------------------------------------------------------------
 
 -- Which apps a user may administer. `admin` is just another app: holding it is
--- what lets someone manage users and invitations. `role` is reserved for
--- per-app roles later and is 'admin' for every row today.
+-- what lets someone manage users and invitations. A permission is (app, role);
+-- `access` is the only role today, and the key admits several per app so finer
+-- ones can be added by inserting rows rather than by migrating this table.
 CREATE TABLE IF NOT EXISTS `user_app_permissions` (
 	`user_id`    VARCHAR(36) NOT NULL,
 	`app`        ENUM('calendar','feedback','tickets','admin') NOT NULL,
-	`role`       VARCHAR(32) NOT NULL DEFAULT 'admin',
+	-- One row per (user, app, role). `access` means "may use this app at all"
+	-- and is the only role today; the key allows several per app so a finer
+	-- permission can be added later by inserting rows, not by migrating.
+	`role`       VARCHAR(32) NOT NULL DEFAULT 'access',
 	`granted_by` VARCHAR(36) DEFAULT NULL,
 	`granted_at` DATETIME    NOT NULL DEFAULT CURRENT_TIMESTAMP,
-	PRIMARY KEY (`user_id`, `app`),
+	-- (user_id, app) is the leftmost prefix of this key, so the per-request
+	-- permission lookup needs no separate index.
+	PRIMARY KEY (`user_id`, `app`, `role`),
 	CONSTRAINT `uap_user_fk` FOREIGN KEY (`user_id`) REFERENCES `user` (`id`) ON DELETE CASCADE
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
 
@@ -133,7 +139,7 @@ CREATE TABLE IF NOT EXISTS `invitations` (
 	`email`       VARCHAR(255) NOT NULL,
 	`name`        VARCHAR(255) NOT NULL,
 	`token_hash`  CHAR(64)     NOT NULL,
-	`apps`        JSON         NOT NULL,
+	`permissions` JSON         NOT NULL,
 	`invited_by`  VARCHAR(36)  DEFAULT NULL,
 	`created_at`  DATETIME     NOT NULL DEFAULT CURRENT_TIMESTAMP,
 	`expires_at`  DATETIME     NOT NULL,