Add email sending (service + 3 flows) and a general asset label generator

Email: a stdlib SMTP mailer (settings-first config, graceful no-op when
unconfigured), a test-email endpoint wired to the Email settings page,
forced first-login password change (users.mustchangepassword, migration
7d23, /change-password flow), new-user welcome mail, and on-demand
report/alert delivery (POST /api/reports/email + Email Report buttons)
with an external-cron-with-a-scoped-PAT path documented for automation.
All tests patch smtplib - no network.

Labels: a shared /print/asset-label/<type>/<id> view any asset detail
page opens - card or plain style, QR or barcode, configurable encoding.
Per-type qr_target_* templates plus label_default_style/codetype/encodes
settings on the Printing page. Measuring-tool labels default to encoding
their inspection-operation code (derived from the location name, e.g.
0615), so every tool in an area shares the area code - verified by
decoding the rendered QR. Machine labels default to the machine number;
blank-serial handled gracefully.

808 tests pass; both features verified live.

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

frontend/src/views/settings/EmailSettings.vue

@@ -162,6 +162,7 @@
 import { onMounted, ref, computed } from 'vue'
 import { useSystemSettings } from '../../composables/systemSettings'
 import { apiError } from '../../utils/apiError'
+import { settingsApi } from '../../api'
 
 const {
   settings, saving, error, success,
@@ -189,18 +190,25 @@ const canTestEmail = computed(() => {
 })
 
 async function testEmail() {
-  // TODO: Implement test email endpoint
   testingEmail.value = true
   error.value = ''
   success.value = ''
   try {
-    // await settingsApi.testEmail()
-    success.value = 'Test email feature coming soon'
+    // Send to the configured Alert Recipients (the endpoint splits the list).
+    const response = await settingsApi.testEmail(settings.alert_recipients)
+    const result = response.data?.data || {}
+    if (result.sent) {
+      success.value = `Test email sent to ${settings.alert_recipients}`
+    } else {
+      error.value = result.error
+        ? `Test email failed: ${result.error}`
+        : (response.data?.message || 'Email is not configured')
+    }
   } catch (e) {
     error.value = apiError(e, 'Failed to send test email')
   } finally {
     testingEmail.value = false
-    setTimeout(() => { success.value = '' }, 3000)
+    setTimeout(() => { success.value = '' }, 4000)
   }
 }