feat(plans): reactivate + delete-when-unused; card layout fixes overlap

Addresses three issues with the plan catalog screen:

1. Retired plans had NO actions (the action cell was gated on "current
   version", which a retired plan lacks) — so there was no way to make one
   in-force again. Add POST /:planId/reactivate (inverse of retire) + a
   Reactivate button on retired plans.

2. No delete. Add DELETE /:planId, allowed ONLY when zero subscriptions
   reference the planId (any version) — a referenced plan version must survive
   for reproducible repricing/audit, so an in-use delete returns 409 and the UI
   says "retire it instead". The Delete button only shows when the plan has 0
   subscribers.

3. The 6-column table overflowed max-w-3xl: action buttons overlapped and the
   status badges wrapped to a second line. Replace it with a CARD list (one card
   per planId, grouped across versions): name + status on top, price · hours ·
   effective on a wrap row, "used by N" expandable to holder names, and actions
   on their own bordered row — nothing overlaps, badges stay inline.

Build+lint 12/12 (i18n parity). Verified on a DB copy: unused plans report
deletable; retire→reactivate flips active back.

Claude-Session: https://claude.ai/code/session_01Xcm6ikLgGoCxxHrxtjkk5V

apps/web/src/lib/i18n/en.ts

@@ -464,8 +464,16 @@ export const en: Catalog = {
     subscribers: "Subscribers",
     inForce: "in force",
     retired: "retired",
+    versionCount: "{{count}} versions",
     newVersion: "New version",
     retire: "Retire",
+    reactivate: "Reactivate",
+    delete: "Delete",
+    deleteTitle: "Delete this plan permanently (only when no subscription uses it)",
+    reactivated: "“{{name}}” is sellable again.",
+    confirmDelete: "Delete the plan “{{name}}” permanently? This can't be undone.",
+    deleted: "Plan “{{name}}” deleted.",
+    deleteInUse: "Can't delete — subscriptions still use this plan. Retire it instead.",
     newTitle: "New plan",
     newVersionTitle: "Publish new version",
     newVersionHint: "This publishes a NEW version of the plan — existing sales keep their original price.",