feat(suppliers)!: full customers model - structured address + custom fields

The dodavatele modal is now an exact mirror of the customers modal
(minus the PDF field-order picker): Nazev+ARES, Ulice, Mesto+PSC, Zeme,
ICO+ARES, DIC, and the same "Vlastni pole" editor (maxWidth md).

Two migrations on sklad_suppliers:
- structured street/city/postal_code/country replace the free-text
  address blob (best-effort split: street / PSC regex / city)
- custom_fields LONGTEXT replaces contact_person/email/phone/notes;
  existing values are preserved as labeled custom fields

The encode/decode of the custom_fields blob is shared with customers
via the new utils/custom-fields.ts. The PO PDF supplier block renders
the structured address + custom-field lines like the customer block;
the supplier picker/detail selects and types follow. Legacy clients
sending the dropped keys are silently stripped (tested). Suppliers
list shows Ulice/Mesto instead of the dropped contact columns; search
covers name/ico/city.

BREAKING CHANGE: sklad_suppliers.address, contact_person, email,
phone, notes columns dropped (data migrated); deploy must run
prisma migrate deploy + generate.

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

src/routes/admin/customers.ts

@@ -9,48 +9,20 @@ import {
   CreateCustomerSchema,
   UpdateCustomerSchema,
 } from "../../schemas/customers.schema";
+import {
+  encodeCustomFields,
+  decodeCustomFields as decodeCustomFieldsShared,
+} from "../../utils/custom-fields";
 
 const ALLOWED_SORT_FIELDS = ["id", "name", "company_id", "city", "country"];
 
-/** Encode custom_fields + customer_field_order into a single JSON blob (matching PHP format) */
-function encodeCustomFields(
-  fields: unknown,
-  fieldOrder: unknown,
-): string | null {
-  const f = Array.isArray(fields) ? fields : [];
-  const o = Array.isArray(fieldOrder) ? fieldOrder : [];
-  if (f.length === 0 && o.length === 0) return null;
-  return JSON.stringify({ fields: f, field_order: o });
-}
-
-/** Decode custom_fields JSON blob into separate fields + field_order for frontend */
+/** Customer-shaped wrapper over the shared codec (field_order key naming). */
 function decodeCustomFields(raw: string | null): {
   custom_fields: unknown[];
   customer_field_order: string[];
 } {
-  if (!raw) return { custom_fields: [], customer_field_order: [] };
-  try {
-    const parsed = JSON.parse(raw);
-    // PHP format: { fields: [...], field_order: [...] }
-    if (
-      parsed &&
-      typeof parsed === "object" &&
-      !Array.isArray(parsed) &&
-      "fields" in parsed
-    ) {
-      return {
-        custom_fields: parsed.fields || [],
-        customer_field_order: parsed.field_order || [],
-      };
-    }
-    // Legacy TS format: raw array
-    if (Array.isArray(parsed)) {
-      return { custom_fields: parsed, customer_field_order: [] };
-    }
-    return { custom_fields: [], customer_field_order: [] };
-  } catch {
-    return { custom_fields: [], customer_field_order: [] };
-  }
+  const { custom_fields, field_order } = decodeCustomFieldsShared(raw);
+  return { custom_fields, customer_field_order: field_order };
 }
 
 export default async function customersRoutes(