feat: remove app name and logo customization feature

Users can no longer customize the app name or logo. The branding API
endpoints, permission, frontend UI, env vars (APP_NAME, MAX_LOGO_SIZE_KB),
and all related tests are removed. Includes a migration to clean up
branding data from existing databases.

apps/api/drizzle/0010_remove_branding.sql

@@ -0,0 +1,14 @@
+-- Remove branding:manage from built-in admin role permissions
+UPDATE `roles`
+SET `permissions` = REPLACE(`permissions`, '"branding:manage",', ''),
+    `updated_at` = unixepoch()
+WHERE `id` = 'builtin-admin';
+--> statement-breakpoint
+-- Remove branding:manage from any custom roles that have it
+UPDATE `roles`
+SET `permissions` = REPLACE(REPLACE(`permissions`, ',"branding:manage"', ''), '"branding:manage",', ''),
+    `updated_at` = unixepoch()
+WHERE `id` != 'builtin-admin' AND `permissions` LIKE '%branding:manage%';
+--> statement-breakpoint
+-- Clean up branding-related settings
+DELETE FROM `settings` WHERE `key` IN ('customLogo', 'appName');