feat(skatt): setup gates + auto-loading momsdeklaration across Skatt & bokslut tabs (#885)

* feat(skatt): setup gates + auto-loading momsdeklaration across Skatt & bokslut tabs

Every tab in the Skatt & bokslut nav group now tells an unconfigured user
what is missing and where to fix it, instead of dead-ending or rendering
zeros:

- Momsdeklaration: gates on vat_registered with a settings CTA; auto-fetches
  the configured period on load and on every period change (no more "Hämta"
  button); one period control (räkenskapsår picked inline for helårsmoms,
  shell selector + back link dropped via new ReportDescriptor.standalone);
  raw <select>s replaced with the Select primitive; banner when moms_period
  is missing; BankID connect returns to the page instead of the report
  library.
- Deadlines: callout (sv+en) when no system-generated tax deadlines exist —
  they are derived from tax settings, so point at /settings/tax rather than
  presenting an empty manual todo list.
- Årsbokslut: "no räkenskapsår yet" (CTA to bookkeeping settings) is now
  distinguished from "nothing to close yet".
- Skattekonto: non-auth fetch failures render an error card with retry
  instead of the misleading "inget saldo hämtat ännu" empty state.

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

* fix(skatt): address bot review — res.ok guard, blocking moms_period gate, panel hidden while räkenskapsår unresolved

- Auto-fetch treats non-2xx or unparsable responses as errors (with retry)
  instead of rendering undefined data.
- momsPeriodMissing now blocks the declaration (EmptyState + settings CTA)
  rather than fetching a guessed quarterly period behind a banner — a
  declaration submittable for the wrong period type is a hazard, not a
  convenience.
- SkatteverketPanel is not rendered while yearly mode awaits a fiscal
  period, so its actions can never target an unconfirmed period.

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

---------

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

lib/reports/catalog.ts

@@ -69,6 +69,12 @@ export interface ReportDescriptor {
   dimensions?: boolean
   /** Only shown when company_settings.dimensions_enabled is true. */
   needsDimensions?: boolean
+  /**
+   * Nav-promoted page that happens to render in the focused-report shell.
+   * Hides the report-library back link and the shell's fiscal-year selector —
+   * the view owns all of its period controls.
+   */
+  standalone?: boolean
 }
 
 /** Categories shown in the legacy desktop rail, in order. */
@@ -206,6 +212,9 @@ export const REPORT_CATALOG: ReportDescriptor[] = [
     category: 'tax_vat',
     params: 'calendar',
     exports: ['xlsx'],
+    // Promoted to the Skatt & bokslut nav group — reached directly, not via
+    // the report library, and it manages its own period selection.
+    standalone: true,
   },
   {
     slug: 'periodisk-sammanstallning',