fix(hr): correct document-expiry date formulas — CEL has no Timestamp+int (#93)

`hr_document.is_expiring_soon` and `expiry_status` used `today() + 30` /
`today() + 60` to build the reminder windows. The formula engine is CEL,
where dates are Timestamps and there is no `Timestamp + int` operator — so
`today() + 30` evaluated to null and every comparison against it silently
failed. Net effect: `is_expiring_soon` was always false and `expiry_status`
never returned the `expiring_30d` / `expiring_60d` bands (only expired / valid
/ none), so the expiry-reminder flow had nothing to fire on.

Fix — use the `daysFromNow(n)` builtin (which returns the Timestamp n days
out) instead of `today() + n`:

    expires_at <= daysFromNow(30)      // was (today() + 30)
    expires_at <= daysFromNow(60)      // was (today() + 60)

Boot-verified against a fresh dev server (@objectstack 15.1.1, 0 errors) —
the seeded documents now band correctly:
- expires in ~15d  → is_expiring_soon = true,  expiry_status = expiring_30d
- expires next year → is_expiring_soon = false, expiry_status = valid
- expired 10d ago   → is_expired = true,        expiry_status = expired
- no expiry date     → expiry_status = none

Note: `hr_employee.tenure_years` has a related but distinct defect
(`floor((today() - hire_date) / 365)` — CEL has neither `Timestamp - Timestamp`
→ number nor a `floor` builtin, and the intended `daysBetween()` primitive is
declared in @objectstack/formula's type list but not wired into the runtime,
so it returns null). That one can't be fixed at the template level without a
working date-diff builtin, so it is intentionally left for a framework
follow-up rather than worked around with an unreadable bucketed ternary.


Claude-Session: https://claude.ai/code/session_01BZguyAaQbyUpwMZ2gMLaAP

Co-authored-by: Claude <noreply@anthropic.com>

Author: os-zhuang

packages/hr/src/objects/hr_document.object.ts

@@ -48,7 +48,10 @@ export const EmployeeDocument = ObjectSchema.create({
     }),
     is_expiring_soon: Field.formula({
       label: 'Expiring Soon?',
-      expression: F`record.expires_at != null && record.expires_at >= today() && record.expires_at <= (today() + 30)`,
+      // `daysFromNow(30)`, not `today() + 30`: the CEL formula engine has no
+      // `Timestamp + int` operator, so `today() + 30` evaluates to null and the
+      // whole comparison silently fails. Day offsets go through the builtin.
+      expression: F`record.expires_at != null && record.expires_at >= today() && record.expires_at <= daysFromNow(30)`,
     }),
     is_expired: Field.formula({
       label: 'Expired?',
@@ -57,7 +60,9 @@ export const EmployeeDocument = ObjectSchema.create({
     expiry_status: Field.formula({
       label: 'Expiry Status',
       description: 'Single severity band for sorting/colour-coding the document list.',
-      expression: F`record.expires_at == null ? "none" : (record.expires_at < today() ? "expired" : (record.expires_at <= (today() + 30) ? "expiring_30d" : (record.expires_at <= (today() + 60) ? "expiring_60d" : "valid")))`,
+      // `daysFromNow(N)`, not `today() + N`: CEL has no `Timestamp + int` operator
+      // (see is_expiring_soon above), so the offset bands must use the builtin.
+      expression: F`record.expires_at == null ? "none" : (record.expires_at < today() ? "expired" : (record.expires_at <= daysFromNow(30) ? "expiring_30d" : (record.expires_at <= daysFromNow(60) ? "expiring_60d" : "valid")))`,
     }),
     notes: Field.markdown({ label: 'Notes' }),
   },