fix(arsredovisning): make the aktiekapital note completable via compa… (#1118)

* fix(arsredovisning): make the aktiekapital note completable via company settings

The annual report warned every AB that the aktiekapital note was missing
and pointed at Installningar -> Foretag, but the referenced columns
(aktiekapital, antal_aktier, kvotvarde) never existed and no settings UI
was ever built, so the warning was a dead end and no AB could produce a
complete note before Bolagsverket filing.

- migration 20260723103000: company_settings.aktiekapital (numeric) and
  antal_aktier (integer) with positive CHECKs; kvotvarde is intentionally
  not stored since ABL 1 kap 6 defines it as aktiekapital / antal aktier
- build-data.ts (K2 and K3 note paths): select only the two stored
  columns and derive kvotvarde with roundOre
- UpdateSettingsSchema: aktiekapital (positive), antal_aktier (positive
  integer), both nullable to allow clearing
- new ShareCapitalForm section on Installningar -> Foretag, rendered for
  aktiebolag only, with live derived kvotvarde display; wired through the
  existing CompanySettingsContent save path (empty string clears to null)
- sv/en strings; settings route tests (round-trip, clear, 400 on invalid);
  builder tests for derived kvotvarde and the empty-settings warning

Staging (metjnjrhvujscngnpzdv) already has the columns applied and the
note verified end-to-end against a rehearsal company.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(arsredovisning): address PR review findings on the share-capital note

- enforce aktiekapital/antal_aktier as an all-or-nothing pair (DB CHECK,
  K2/K3 note guard now requires both, partial pair warns instead)
- numeric(15,2) column, .int() Zod constraint, maxFractionDigits 0 render
- guard numberOrNull against NaN; align kvotvarde preview with schema
- strengthen clearing test, add fractional and partial-pair tests

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

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

app/api/settings/__tests__/route.test.ts

@@ -97,6 +97,54 @@ describe('PUT /api/settings', () => {
     expect(deadlineMocks.regenerate).not.toHaveBeenCalled()
   })
 
+  it('round-trips share capital fields and clears them with null', async () => {
+    const updates = { aktiekapital: 25000, antal_aktier: 500 }
+    enqueueMany([
+      { data: { entity_type: 'aktiebolag', onboarding_complete: true } },
+      { data: { id: 's1', ...updates } },
+      { data: null, count: 5 },
+    ])
+
+    const response = await PUT(createMockRequest('/api/settings', {
+      method: 'PUT',
+      body: updates,
+    }), { params: Promise.resolve({}) })
+    const { status, body } = await parseJsonResponse<{ data: typeof updates }>(response)
+
+    expect(status).toBe(200)
+    expect(body.data).toMatchObject(updates)
+
+    enqueueMany([
+      { data: { entity_type: 'aktiebolag', onboarding_complete: true } },
+      { data: { id: 's1', aktiekapital: null, antal_aktier: null } },
+      { data: null, count: 5 },
+    ])
+    const clearResponse = await PUT(createMockRequest('/api/settings', {
+      method: 'PUT',
+      body: { aktiekapital: null, antal_aktier: null },
+    }), { params: Promise.resolve({}) })
+    const cleared = await parseJsonResponse<{ data: Record<string, unknown> }>(clearResponse)
+    expect(cleared.status).toBe(200)
+    expect(cleared.body.data.aktiekapital).toBeNull()
+    expect(cleared.body.data.antal_aktier).toBeNull()
+  })
+
+  it('rejects non-positive aktiekapital and fractional antal_aktier', async () => {
+    for (const body of [
+      { aktiekapital: 0 },
+      { aktiekapital: -25000 },
+      { aktiekapital: 25000.5 },
+      { antal_aktier: 0 },
+      { antal_aktier: 500.5 },
+    ]) {
+      const response = await PUT(createMockRequest('/api/settings', {
+        method: 'PUT',
+        body,
+      }), { params: Promise.resolve({}) })
+      expect((await parseJsonResponse(response)).status).toBe(400)
+    }
+  })
+
   it('updates invoice email recipients and payment accounts', async () => {
     const updates = {
       invoice_email_cc_addresses: ['info@example.com', 'owner@example.com'],