refactor(ui): record detail pages as documents, not card piles (#1739)

Bring every record detail page onto the register-detail document grammar
from #1624 (DetailSection/DefRow, one status element per the list pages'
chips-mark-exceptions rule, one primary next step plus Förhandsgranska
visible and everything else behind a ⋯ overflow menu, line tables on the
dry-table idiom with the headline total in the serif):

- invoices/[id] (11 cards, 13-button toolbar): Kund | Detaljer rows,
  Fakturarader table + totals, Anteckningar, Betalning, Påminnelser,
  Utskickshistorik (InvoiceDeliveryHistory flattened); title carries the
  doc type, related documents become link rows
- supplier-invoices/[id], bookkeeping/[id] (serif title instead of
  font-mono, JournalEntryAttachments variant="section", CorrectionChain
  flattened), invoices/[id]/credit, assets/[id]/dispose (form as Fönster
  rows), salary employees/[id] (edit form behind Redigera in a dialog,
  Ingående saldon collapsed), salary runs/[id] + run panels (Betalfil,
  Skattebetalning, AGI, förmåner, override) and the payslip page
- DetailSection gains an optional help slot (convention 7)

Styling/structure only: no API, fetch, validation, state, dialog or
permission change; every action stays reachable.

Co-authored-by: Jakob Wennberg <311770904+jakobwennberg-oss@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

components/ui/detail-section.tsx

@@ -11,11 +11,14 @@ import { cn } from '@/lib/utils'
 
 export function DetailSection({
   kicker,
+  help,
   aside,
   children,
   className,
 }: {
   kicker: string
+  /** Section help behind a "?" right after the kicker (convention 7). Pass a <HelpPopover>. */
+  help?: React.ReactNode
   /** Optional right-aligned element on the kicker line: a count, a quiet action. */
   aside?: React.ReactNode
   children: React.ReactNode
@@ -25,8 +28,9 @@ export function DetailSection({
     <section className={className}>
       <div className="flex items-baseline justify-between gap-4 border-b border-border pb-2">
         {/* data-ph-unmask: kickers are static i18n chrome in session replays. */}
-        <h2 data-ph-unmask="" className="text-[11px] font-medium uppercase tracking-wider text-muted-foreground">
+        <h2 data-ph-unmask="" className="flex items-center gap-2 text-[11px] font-medium uppercase tracking-wider text-muted-foreground">
           {kicker}
+          {help}
         </h2>
         {aside}
       </div>