feat(supplier-invoices): sortable list columns matching the customer invoice list (#2091)

Adds client-side sorting to /supplier-invoices: all seven columns get the
same accessible SortableHeader as /invoices, backed by a pure comparator
(Swedish collation, nulls last, displayed-value semantics, stable
invoice_date/id tie-break). The click cycle is tri-state (asc, desc, back
to the API default of due date ascending) per the verifikat-list
precedent, since this list has a meaningful default order to return to.
The detail-pager list context follows the sorted order.


Claude-Session: https://claude.ai/code/session_01DZSVsZqbx8vDnC2SXunNaR

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

messages/en.json

@@ -918,6 +918,7 @@
     "th_amount": "Amount",
     "th_remaining": "Remaining",
     "th_status": "Status",
+    "sort_by": "Sort by {column}",
     "status_registered": "Registered",
     "status_approved": "Approved",
     "status_paid": "Paid",

messages/sv.json

@@ -918,6 +918,7 @@
     "th_amount": "Belopp",
     "th_remaining": "Kvar att betala",
     "th_status": "Status",
+    "sort_by": "Sortera efter {column}",
     "status_registered": "Registrerad",
     "status_approved": "Godkänd",
     "status_paid": "Betald",