feat(sub): allow identity tokens on every subscription link (#5935)

Keep usage tokens first-link-only while adding an opt-in setting for repeating EMAIL and USERNAME in subscription-body remarks.

Co-authored-by: x06579 <x06579@ai-dashboard>

frontend/src/test/setting-sub-identity.test.ts

@@ -0,0 +1,22 @@
+import { describe, it, expect } from 'vitest';
+import { AllSettingSchema } from '@/schemas/setting';
+import { AllSetting } from '@/models/setting';
+
+describe('subShowIdentityOnAllLinks', () => {
+  it('defaults to false on AllSetting', () => {
+    expect(new AllSetting().subShowIdentityOnAllLinks).toBe(false);
+  });
+
+  it('accepts boolean values in the settings schema', () => {
+    for (const v of [true, false]) {
+      const r = AllSettingSchema.safeParse({ subShowIdentityOnAllLinks: v });
+      expect(r.success, `subShowIdentityOnAllLinks=${v}`).toBe(true);
+    }
+  });
+
+  it('rejects non-boolean values', () => {
+    for (const v of ['true', 1, null]) {
+      expect(AllSettingSchema.safeParse({ subShowIdentityOnAllLinks: v }).success).toBe(false);
+    }
+  });
+});