feat(licserver): add partner API proxy routes and types

- New: lib/types/licserver.ts (PartnerDto, paged result, problem)
- New: app/api/licserver/partners/route.ts (GET search/list)
- New: app/api/licserver/partners/[id]/route.ts (GET by UUID)
- Updated: .env.example with LICSERVER_BASE_URL + LICSERVER_API_KEY

Auth-guarded via Supabase session. API key is server-side only.
Upstream: http://192.168.178.174:9980 (internal container network)

shop/lib/types/licserver.ts

@@ -0,0 +1,31 @@
+/**
+ * TypeScript types generated from the CASPOS LicServer OpenAPI spec v1.
+ * Source: /api-v1/partners endpoints
+ */
+
+export interface PartnerDto {
+  id: string          // UUID
+  name:  string | null
+  email: string | null
+  erpId: string | null
+}
+
+export interface PartnerDtoPagedResult {
+  page:            number
+  pageSize:        number
+  totalCount:      number
+  totalPages:      number
+  hasNextPage:     boolean
+  hasPreviousPage: boolean
+  items:           PartnerDto[] | null
+}
+
+/** Standard RFC 7807 problem response from LicServer */
+export interface LicServerProblemDetails {
+  type?:     string | null
+  title?:    string | null
+  status?:   number | null
+  detail?:   string | null
+  instance?: string | null
+  [key: string]: unknown
+}