feat: show Jobs tab for all vendors when no filter selected

- Add /admin/letzshop/jobs API endpoint for all jobs across vendors
- Update list_letzshop_jobs service to support optional vendor_id
- Remove x-if condition from Jobs tab button and panel
- Update JS to use global or vendor-specific endpoint based on selection
- Update jobs table subtitle to show context

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

static/admin/js/marketplace-letzshop.js

@@ -158,7 +158,8 @@ function adminMarketplaceLetzshop() {
             // Watch for tab changes to reload relevant data
             this.$watch('activeTab', async (newTab) => {
                 marketplaceLetzshopLog.info('Tab changed to:', newTab);
-                if (newTab === 'jobs' && this.selectedVendor) {
+                if (newTab === 'jobs') {
+                    // Load jobs for selected vendor or all Letzshop jobs
                     await this.loadJobs();
                 } else if (newTab === 'products') {
                     // Load products for selected vendor or all Letzshop products
@@ -1418,17 +1419,9 @@ function adminMarketplaceLetzshop() {
         },
 
         /**
-         * Load jobs for selected vendor
-         * Note: Jobs are vendor-specific, so we need a vendor selected to show them
+         * Load jobs for selected vendor or all vendors
          */
         async loadJobs() {
-            // Jobs require a vendor to be selected (they are vendor-specific)
-            if (!this.selectedVendor) {
-                this.jobs = [];
-                this.jobsPagination.total = 0;
-                return;
-            }
-
             this.loadingJobs = true;
 
             try {
@@ -1444,7 +1437,12 @@ function adminMarketplaceLetzshop() {
                     params.append('status', this.jobsFilter.status);
                 }
 
-                const response = await apiClient.get(`/admin/letzshop/vendors/${this.selectedVendor.id}/jobs?${params}`);
+                // Use vendor-specific or global endpoint based on selection
+                const endpoint = this.selectedVendor
+                    ? `/admin/letzshop/vendors/${this.selectedVendor.id}/jobs?${params}`
+                    : `/admin/letzshop/jobs?${params}`;
+
+                const response = await apiClient.get(endpoint);
                 this.jobs = response.jobs || [];
                 this.jobsPagination.total = response.total || 0;
             } catch (error) {