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/composables/systemSettings.js

@@ -87,6 +87,17 @@ export function useSystemSettings() {
     qr_target_printer: '',
     qr_target_usb: '',
     usb_label_style: 'barcode',
+    qr_target_machine: '',
+    qr_target_computer: '',
+    qr_target_network_device: '',
+    qr_target_measuring_tool: '',
+    label_default_style: 'card',
+    label_default_codetype: 'qr',
+    label_default_encodes_machine: 'assetnumber',
+    label_default_encodes_computer: 'assetpage',
+    label_default_encodes_printer: 'assetpage',
+    label_default_encodes_network_device: 'assetpage',
+    label_default_encodes_measuring_tool: 'location',
     // Email
     smtp_enabled: false,
     smtp_host: '',