Add/user feedback (#679)

* feat(bookkeeping): make blocked fiscal-year creation actionable

When creating a new räkenskapsår is blocked because a prior period is
still open, the "Skapa räkenskapsår" dialog no longer dead-ends on an
English toast. The API now returns the canonical bilingual error envelope
with the blocking periods (id/name/dates) under details, and the dialog
renders a Swedish panel that locks them inline (reversible locked_at) via
the existing /lock endpoint and retries creation.

The guard rule is unchanged and remains BFL-compliant: BFL 6 kap allows
löpande bokföring of the new year in parallel with the prior year's
bokslut, so a lock (not a full close) is sufficient and reversible.

- Add PERIOD_CREATE_BLOCKED_BY_OPEN_PERIODS structured error code
- Return envelope + details.blockingPeriods from the 409 (was English string)
- CreatePeriodDialog: inline "lås och skapa" panel + lock-and-retry
- Update route tests for the new envelope shape

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(ui): prevent mouse wheel from mutating number inputs

A focused <input type="number"> would change its value on scroll,
silently turning e.g. a 20000 salary into 19998. Blur number inputs
on wheel so the page scrolls instead of editing the value. Applied
at the Input primitive so all number fields are protected.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* feat(salary): auto-derive skattetabell and kolumn for employees

Replace the opaque manual "Skattetabell (29-42)" and "Kolumn (1-6)" inputs
on the employee form with a self-deriving flow: the user picks their
folkbokföringskommun from a searchable dropdown and the tax table fills
itself in, while the column derives from the personnummer we already collect.

- Add a searchable municipality picker (MunicipalityCombobox) backed by a
  new cached GET /api/salary/tax-tables/kommuner endpoint.
- Wrap the whole "Skatt" card in a self-contained EmployeeTaxCard used by
  both the create and edit pages, with InfoTooltips and named column options.
- deriveTaxColumn(): auto-select column 1 for under-66 employees; leave the
  ambiguous 66+ case (pension vs working senior) to a clearly-named manual
  choice.
- Fix fetchKommunTaxRates() to page through all ~1300 församling rows instead
  of a single 500-row page (which silently dropped ~200 kommuner, incl.
  Göteborg) and normalize the uppercase names to title case.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* fix(import): correct CSV amount-column guess and surface skipped rows

Manual CSV column-mapping auto-guess walked each data row right-to-left
and picked the first numeric cell as the amount, so on the common
...;Belopp;Saldo layout it grabbed the trailing running-balance column.
Extract the guess into a pure, tested suggestColumnMapping(): match
header labels first (belopp/amount -> amount, saldo/balance -> balance),
auto-fill the balance field, and fall back to value heuristics that skip
the balance column and prefer a column carrying negative values.

Also surface stats.skipped_rows + parse warnings in BankFileConfirmStep -
the manual-mapping path skips the preview step that was the only place
they showed, so skipped rows were silently dropped from view.

Add a unit test reproducing the Saldo-as-amount regression.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* feat: add "Save as draft" functionality for invoices

- Implemented a new feature to allow users to save invoices as unnumbered drafts without generating an invoice number until finalized.
- Added a `save_as_draft` flag to the CreateInvoiceInput schema to handle draft saving logic.
- Updated the invoice creation API to skip number allocation when saving as a draft.
- Introduced a new endpoint for finalizing drafts, which allocates an invoice number and emits an `invoice.created` event.
- Enhanced the UI to include a "Save as draft" button, with loading states and tooltips.
- Updated tests to cover the new draft saving and finalization logic, including race conditions for concurrent modifications.
- Added relevant error handling for draft finalization and deletion scenarios.

* feat(employee): add employment start and end date fields to employee forms

* feat: enhance invoice and salary run handling with improved validation and event logging

---------

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/errors/structured-errors.ts

@@ -738,6 +738,21 @@ const INVOICE: Record<string, StructuredErrorEntry> = {
     message_sv: 'Fakturan ändrades samtidigt och kunde inte makuleras. Ladda om och försök igen.',
     message_en: 'Invoice was modified concurrently and could not be cancelled. Reload and retry.',
   },
+  INVOICE_NOT_FOUND: {
+    httpStatus: 404,
+    message_sv: 'Fakturan kunde inte hittas.',
+    message_en: 'Invoice not found.',
+  },
+  INVOICE_FINALIZE_NOT_DRAFT: {
+    httpStatus: 409,
+    message_sv: 'Endast onumrerade utkast kan skapas. Fakturan har redan ett nummer eller är inte ett utkast.',
+    message_en: 'Only unnumbered drafts can be finalized; this invoice already has a number or is not a draft.',
+  },
+  INVOICE_FINALIZE_INCOMPLETE: {
+    httpStatus: 500,
+    message_sv: 'Fakturanumret tilldelades men fakturan kunde inte läsas tillbaka. Ladda om sidan och kontrollera fakturan.',
+    message_en: 'The invoice number was assigned but the invoice could not be re-read. Reload the page and verify the invoice.',
+  },
   // Quotes / Offerter
   QUOTE_NOT_FOUND: {
     httpStatus: 404,
@@ -833,6 +848,20 @@ const PERIOD: Record<string, StructuredErrorEntry> = {
     message_sv: 'Perioden är redan låst.',
     message_en: 'Period is already locked.',
   },
+  // Forward-chaining a new räkenskapsår is blocked while a prior period is
+  // still fully open (not locked, not closed, not covered by the company-wide
+  // lock-through date). BFL 6 kap allows löpande bokföring of the new year in
+  // parallel with bokslut, but the prior year must at least be locked so
+  // nothing is back-posted into a year you've moved on from. The blocking
+  // periods (id + name + dates) are attached to the response `details` so the
+  // UI can offer to lock them inline. See app/api/bookkeeping/fiscal-periods.
+  PERIOD_CREATE_BLOCKED_BY_OPEN_PERIODS: {
+    httpStatus: 409,
+    message_sv:
+      'Du måste låsa föregående räkenskapsår innan du kan skapa ett nytt.',
+    message_en:
+      'Cannot create a new fiscal year while a prior period is still open; lock it first.',
+  },
 }
 
 const YEAR_END: Record<string, StructuredErrorEntry> = {