Bug/document linking (#688)

* feat: enhance supplier invoice payment process and settings handling

- Implemented linking of invoice documents to journal entries for cash payments in the supplier invoice payment process.
- Refactored settings fetching logic to improve loading states and error handling across various settings components.
- Introduced a new SettingsLoadError component to handle cases where settings fetch fails or returns no data.
- Updated useSettings hook to manage loading and error states more effectively, allowing for retries on failure.
- Enhanced tests for supplier invoice creation to ensure document IDs are persisted correctly for cash method payments.

* feat(salary): enable monthly salary edits in draft runs and handle zero-total declarations

lib/api/schemas.ts

@@ -1738,6 +1738,11 @@ const SALARY_OVERRIDE_MAX = 10_000_000
 
 export const SalaryEmployeeOverrideSchema = z
   .object({
+    // Per-run monthly salary for this employee, editable while the run is a
+    // draft. 0 is allowed (an intentional nollkörning). This is NOT a review
+    // override — it sets the base the engine uses for this month only and does
+    // not require a reason. The route gates this field to `draft` status.
+    monthly_salary: z.number().nonnegative().max(SALARY_OVERRIDE_MAX).optional(),
     tax_withheld_override: z.number().nonnegative().max(SALARY_OVERRIDE_MAX).nullable().optional(),
     avgifter_amount_override: z.number().nonnegative().max(SALARY_OVERRIDE_MAX).nullable().optional(),
     avgifter_basis_override: z.number().nonnegative().max(SALARY_OVERRIDE_MAX).nullable().optional(),