chore(deps): add rrule for richer medication scheduling cadences

The v1.5 medication-scheduling work needs to model monthly /
quarterly / yearly cadences plus arbitrary `INTERVAL` patterns. The
existing string encoding caps the interval at 4 weeks and has no
representation for month-level recurrence at all. RFC 5545 RRULE is
the industry standard for this and the `rrule` package is the
battle-tested TypeScript implementation (used by Google Calendar
sync, EventKit translation layers, FHIR servers).

Pin the latest stable. The library's release cadence has slowed
since 2022; a future migration to `rrule-temporal` is worth tracking
once Node 24 LTS lands, but the existing surface covers HealthLog's
needs without modification.

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

package.json

@@ -79,6 +79,7 @@
     "react-dom": "19.2.5",
     "react-hook-form": "^7.76.1",
     "recharts": "^3.8.1",
+    "rrule": "^2.8.1",
     "sax": "^1.6.0",
     "sonner": "^2.0.7",
     "tailwind-merge": "^3.6.0",