Add the measuringtools plugin (ADR-005) and the plugin-system tutorial

Gage-lab instruments as Asset extensions: measuringtooltypes (color-coded
lookup) + measuringtools (calibration interval/dates, provider, notes) with
calibration status derived at read time (overdue / due soon / current /
unknown), never stored. Full CRUD API with permission-gated writes, types
management with in-use guard, calibration report, nav/reports/config-schema
hooks, and a complete frontend (list/detail/form, types settings page,
calibration report page, gated routes per ADR-009).

First plugin whose migration chain really creates tables post-cutover
(ADR-008), and the working example for docs/PLUGIN-GUIDE.md - a 12-section
walkthrough of building a plugin on this framework, linked from
PLUGIN-QUICKSTART and PLUGINS.

Verified: full suite 323 passing, live E2E on all four pages, fresh
scratch-MySQL migration dry-run green.

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

frontend/src/router/routes/measuringtools.js

@@ -0,0 +1,46 @@
+/**
+ * Measuring-tools plugin routes.
+ *
+ * Every route carries meta.plugin = 'measuringtools' so the ADR-009 router
+ * guard redirects to the dashboard when the backend plugin is disabled. List
+ * and detail are public (no requiresAuth, matching the other asset types); the
+ * form requires auth; the settings subtype page requires admin.
+ */
+export default [
+  {
+    path: 'measuringtools',
+    name: 'measuringtools',
+    component: () => import('../../views/measuringtools/MeasuringToolsList.vue'),
+    meta: { plugin: 'measuringtools' }
+  },
+  {
+    path: 'measuringtools/new',
+    name: 'measuringtool-new',
+    component: () => import('../../views/measuringtools/MeasuringToolForm.vue'),
+    meta: { requiresAuth: true, plugin: 'measuringtools' }
+  },
+  {
+    path: 'measuringtools/:id',
+    name: 'measuringtool-detail',
+    component: () => import('../../views/measuringtools/MeasuringToolDetail.vue'),
+    meta: { plugin: 'measuringtools' }
+  },
+  {
+    path: 'measuringtools/:id/edit',
+    name: 'measuringtool-edit',
+    component: () => import('../../views/measuringtools/MeasuringToolForm.vue'),
+    meta: { requiresAuth: true, plugin: 'measuringtools' }
+  },
+  {
+    path: 'reports/calibration',
+    name: 'calibration-report',
+    component: () => import('../../views/reports/CalibrationReport.vue'),
+    meta: { plugin: 'measuringtools' }
+  },
+  {
+    path: 'settings/measuringtooltypes',
+    name: 'measuringtooltypes',
+    component: () => import('../../views/settings/MeasuringToolTypesList.vue'),
+    meta: { requiresAuth: true, requiresAdmin: true, plugin: 'measuringtools' }
+  }
+]