feat(cycle): add the calendar-feed credential table

A record's cycle calendar subscription is a URL credential: one row per
feed, only the HMAC of the raw hlf_ token stored, and at most one live
feed per record through a partial unique index on user_id where
revoked_at is null. Both foreign keys cascade, so deleting the record
or the carrier who minted the feed ends it.

The row is a credential everywhere else too. It stays out of the
backup (a restore would bring back a revoked link), Delete All Data
takes it on both sides, a credential remediation revokes the feeds on
the record and the ones the account minted elsewhere, and a
managed-profile handover claim revokes any feed a guardian minted.

backupVerdict moves beside the plan into its own module so the plan
stays the lists and their reasons.

src/__tests__/backup-plan-classification.test.ts

@@ -9,8 +9,8 @@ import {
   DERIVED_MODELS,
   NOT_IN_BACKUP_MODELS,
   RAW_SQL_TABLES,
-  backupVerdict,
 } from "@/lib/export/backup-plan";
+import { backupVerdict } from "@/lib/export/backup-verdict";
 
 /**
  * Every model in the schema has a written verdict about the backup.