feat(dimensions): show the value's name after picking, and let an unused custom dimension be deleted (#2219) (#2255)

* feat(dimensions): show the value's name after picking, and let an unused custom dimension be deleted (#2219)

Two things from the same Discord report, both in bookkeeping from the
transaction view:

1. After picking a kostnadsställe the field showed only the code ("1").
   DimensionCombobox now writes the value's full name under the field once
   a code is committed, exactly as AccountCombobox does for the account
   name (looked up in the full registry so an archived code stays
   readable). The input text itself stays the code: the blur/revert logic
   keys on it.

2. A self-created dimension could not be removed at all: the DB already
   allowed it (enforce_dimension_registry_guards lets a non-system
   dimension go when no posted/reversed line carries its number, and the
   value retention trigger fires on the cascade), but no route or UI
   asked. New DELETE /api/dimensions/[id]: 400 DIMENSION_SYSTEM_DELETE for
   kostnadsställe/projekt, the guard's own Swedish P0001 verbatim as 409
   DIMENSION_REFERENCED, 404, and a happy path; the register gets a quiet
   "Ta bort dimension" link for the active custom dimension behind a
   DestructiveConfirmDialog. Keys added to sv and en.

Closes #2219

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VnConrmMCxJRQ5kfiPPWyy

* test: satisfy the TypeScript ratchet for two test files main inherited from #2247 and #2242

accounts-route.test.ts built SyncResult literals without the
requestedFromDate / historyNarrowed fields #2247 added (vitest does not
typecheck, so it passed locally); fiscal-periods route.test.ts got two
more one-argument POST(req) calls from #2242 in a file already at its
ratchet baseline. Both files now typecheck; the ratchet runs clean.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VnConrmMCxJRQ5kfiPPWyy

---------

Co-authored-by: Jakob Wennberg <311770904+jakobwennberg-oss@users.noreply.github.com>
Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

lib/errors/structured-errors.ts

@@ -4130,6 +4130,31 @@ const DIMENSION: Record<string, StructuredErrorEntry> = {
     message_sv: 'Dimensionen kunde inte uppdateras.',
     message_en: 'Failed to update dimension.',
   },
+  DIMENSION_SYSTEM_DELETE: {
+    httpStatus: 400,
+    message_sv: 'Systemdimensioner (kostnadsställe och projekt) kan inte tas bort: avaktivera dem istället.',
+    message_en: 'System dimensions (kostnadsställe/projekt) cannot be deleted: archive (inactivate) them instead.',
+  },
+  // The DB registry guard (enforce_dimension_registry_guards) raises when any
+  // posted/reversed line is tagged with the dimension's number, and the value
+  // retention trigger fires on the cascade to dimension_values. Routes surface
+  // the trigger's own Swedish message via `messageSv`.
+  DIMENSION_REFERENCED: {
+    httpStatus: 409,
+    message_sv:
+      'Dimensionen används på bokförda verifikat och kan inte tas bort: avaktivera den istället.',
+    message_en:
+      'The dimension is referenced by posted vouchers and cannot be deleted: archive (inactivate) it instead.',
+    remediation: {
+      description:
+        'Archive the dimension instead: PATCH /api/dimensions/[id] with { "is_active": false }. Numbers tagged on posted lines are retained for the BFL 7-year period.',
+    },
+  },
+  DIMENSION_DELETE_FAILED: {
+    httpStatus: 500,
+    message_sv: 'Dimensionen kunde inte tas bort.',
+    message_en: 'Failed to delete dimension.',
+  },
   DIMENSION_VALUE_NOT_FOUND: {
     httpStatus: 404,
     message_sv: 'Dimensionsvärdet kunde inte hittas.',