Dissolve System Settings into individual settings pages

The monolithic tab page competed with the settings rail as a second
navigation system, and its Integrations tab was a dumping ground. Each
section is now its own routed rail page (ServiceNow, Zabbix Supplies,
Dell Warranty, Collector PC Types, Branding, Floor Map, Printing and
Labels, Email/SMTP, Audit, Authentication, Asset Identifiers, Global
Search), thin over a shared useSystemSettings composable, grouped
logically in the rail with system groups clustered last. Old
/settings/system?tab= URLs redirect to the right page.

Also fixes the post-login redirect: the auth guard now remembers the
intended destination and Login returns there (same-site paths only).

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

frontend/src/views/settings/PrintingSettings.vue

@@ -0,0 +1,75 @@
+<template>
+  <div>
+    <div class="page-header">
+      <h2>Printing &amp; Labels</h2>
+    </div>
+
+    <div class="section-card">
+      <div class="setting-group">
+        <p class="setting-description">
+          Where printed QR codes point. Leave a target blank to link to the
+          asset's own page on this instance, or enter a custom URL template
+          with {placeholder} substitution.
+        </p>
+
+        <div class="setting-row">
+          <label>
+            <span>Printer QR target</span>
+            <input
+              type="text"
+              v-model="settings.qr_target_printer"
+              placeholder="(blank = printer page)"
+              @blur="saveSetting('qr_target_printer', settings.qr_target_printer)"
+              :disabled="saving"
+            >
+            <small class="input-hint">Placeholders: {printerid}, {assetid}, {assetnumber}, {serialnumber}, {ip}, {hostname}</small>
+          </label>
+        </div>
+
+        <div class="setting-row">
+          <label>
+            <span>USB label QR target</span>
+            <input
+              type="text"
+              v-model="settings.qr_target_usb"
+              placeholder="(blank = USB device page)"
+              @blur="saveSetting('qr_target_usb', settings.qr_target_usb)"
+              :disabled="saving"
+            >
+            <small class="input-hint">Placeholders: {id}, {serialnumber}, {alias}</small>
+          </label>
+        </div>
+
+        <div class="setting-row">
+          <label>
+            <span>USB label style</span>
+            <select
+              v-model="settings.usb_label_style"
+              @change="saveSetting('usb_label_style', settings.usb_label_style)"
+              :disabled="saving"
+            >
+              <option value="barcode">Barcode (CODE128 of the serial number)</option>
+              <option value="qr">QR code (links to the USB label QR target)</option>
+            </select>
+            <small class="input-hint">Applies to the batch USB mini-label print sheet.</small>
+          </label>
+        </div>
+      </div>
+    </div>
+
+    <div v-if="error" class="error-message">{{ error }}</div>
+    <div v-if="success" class="settings-success">{{ success }}</div>
+  </div>
+</template>
+
+<script setup>
+import { onMounted } from 'vue'
+import { useSystemSettings } from '../../composables/systemSettings'
+
+const {
+  settings, saving, error, success,
+  loadSettings, saveSetting,
+} = useSystemSettings()
+
+onMounted(loadSettings)
+</script>