feat: add health alerts field and delete actions for pets and clients (#25)

- Add health_alerts column to pets table (migration 0001)
- Update DB schema, shared types, and API Zod validation
- Show health alerts prominently (red badge) in pet cards
- Add health alerts field to pet form with allergy/condition placeholder
- Add delete button per pet with confirmation dialog
- Add delete client button with cascade warning

Closes groombook/groombook#2

Co-authored-by: Groom Book CTO <cto@groombook.app>
Co-authored-by: Paperclip <noreply@paperclip.ing>

apps/api/src/routes/pets.ts

@@ -12,6 +12,7 @@ const createPetSchema = z.object({
   breed: z.string().max(200).optional(),
   weightKg: z.number().positive().optional(),
   dateOfBirth: z.string().datetime().optional(),
+  healthAlerts: z.string().max(2000).optional(),
   groomingNotes: z.string().max(2000).optional(),
 });