fix(bookkeeping): editable verifikationstext on andringsverifikation (#1035)

The correction header was always built server-side as
"Rattelse: <original description>". When the original entry was labelled
after the wrong account, the correction kept echoing that stale label even
after the user switched to the correct account (follow-up to the
line-description fix in #1029).

- CorrectJournalEntrySchema gains an optional trimmed description
- correctEntry() accepts options.description; blank or absent falls back
  to the canonical "Rattelse: <original>" auto text
- both correct routes (dashboard + v1, which share the schema) thread the
  description through
- CorrectionEntryDialog surfaces an editable verifikationstext field,
  pre-filled with the auto text; an untouched or cleared prefill is NOT
  sent, so the server-side fallback stays the source of truth (same
  only-overwrite-auto-filled principle as #1029)

Forward-only: already-posted corrections are immutable per BFL.

Fixes #1031

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

lib/api/__tests__/schemas.test.ts

@@ -2212,6 +2212,31 @@ describe('CorrectJournalEntrySchema', () => {
     })
     expect(result.success).toBe(false)
   })
+
+  it('accepts an optional description and trims it', () => {
+    const result = CorrectJournalEntrySchema.safeParse({
+      description: '  Rättelse: Skulder till närstående personer, kortfristig del  ',
+      lines: [
+        validJournalEntryLine({ account_number: '6200', debit_amount: 500, credit_amount: 0 }),
+        validJournalEntryLine({ account_number: '1930', debit_amount: 0, credit_amount: 500 }),
+      ],
+    })
+    expect(result.success).toBe(true)
+    if (result.success) {
+      expect(result.data.description).toBe('Rättelse: Skulder till närstående personer, kortfristig del')
+    }
+  })
+
+  it('rejects a blank description (omit it to use the server fallback)', () => {
+    const result = CorrectJournalEntrySchema.safeParse({
+      description: '   ',
+      lines: [
+        validJournalEntryLine({ account_number: '6200', debit_amount: 500, credit_amount: 0 }),
+        validJournalEntryLine({ account_number: '1930', debit_amount: 0, credit_amount: 500 }),
+      ],
+    })
+    expect(result.success).toBe(false)
+  })
 })
 
 // ============================================================