feat(reminders): cadence-aware framework with auto/manual modes

isReminderDue now keys off doc.remindersDisabled and the effective
cadence (per-doc override → template default), dropping the implicit
interests.reminderEnabled gate so non-EOI docs auto-remind correctly.
sendReminderIfAllowed gains an options bag — auto:true keeps the 9-16
window + cadence cooldown for the cron, auto:false bypasses both for
manual UI sends. signerId targets a specific pending signer (must be
next in sequential mode). 7 unit tests cover the cadence math.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/unit/services/document-reminders-cadence.test.ts

@@ -0,0 +1,70 @@
+import { describe, expect, it } from 'vitest';
+
+import { isReminderDue } from '@/lib/services/document-reminders';
+
+const now = new Date('2026-04-28T12:00:00Z');
+
+function args(overrides: Partial<Parameters<typeof isReminderDue>[0]> = {}) {
+  return {
+    status: 'sent' as const,
+    documensoId: 'doc-1',
+    remindersDisabled: false,
+    reminderCadenceOverride: null,
+    templateCadenceDays: 7,
+    lastReminderAt: null,
+    now,
+    ...overrides,
+  };
+}
+
+describe('isReminderDue', () => {
+  it('returns true when no prior reminder exists and cadence is set', () => {
+    expect(isReminderDue(args())).toBe(true);
+  });
+
+  it('returns false when document is completed', () => {
+    expect(isReminderDue(args({ status: 'completed' }))).toBe(false);
+  });
+
+  it('returns false when document has no Documenso id', () => {
+    expect(isReminderDue(args({ documensoId: null }))).toBe(false);
+  });
+
+  it('returns false when reminders are disabled per-doc', () => {
+    expect(isReminderDue(args({ remindersDisabled: true }))).toBe(false);
+  });
+
+  it('returns false when neither override nor template cadence is set', () => {
+    expect(isReminderDue(args({ templateCadenceDays: null }))).toBe(false);
+  });
+
+  it('respects per-doc override over template default', () => {
+    // 1-day override, last fired 12h ago → not due
+    const lastReminderAt = new Date(now.getTime() - 12 * 60 * 60 * 1000);
+    expect(
+      isReminderDue(args({ templateCadenceDays: 7, reminderCadenceOverride: 1, lastReminderAt })),
+    ).toBe(false);
+
+    // 1-day override, last fired 25h ago → due
+    const earlier = new Date(now.getTime() - 25 * 60 * 60 * 1000);
+    expect(
+      isReminderDue(
+        args({
+          templateCadenceDays: 7,
+          reminderCadenceOverride: 1,
+          lastReminderAt: earlier,
+        }),
+      ),
+    ).toBe(true);
+  });
+
+  it('treats template cadence as the fallback when no override', () => {
+    // 7-day template, last fired 6 days ago → not due
+    const lastReminderAt = new Date(now.getTime() - 6 * 24 * 60 * 60 * 1000);
+    expect(isReminderDue(args({ lastReminderAt }))).toBe(false);
+
+    // 7 days exactly → due
+    const sevenDays = new Date(now.getTime() - 7 * 24 * 60 * 60 * 1000);
+    expect(isReminderDue(args({ lastReminderAt: sevenDays }))).toBe(true);
+  });
+});