feat: add telemetry consent dialog + Settings privacy toggles

First-launch consent dialog asks users to opt-in to anonymous crash
reporting. Settings panel gains Privacy & Telemetry section with
toggles for crash reporting and usage analytics. Consent gate blocks
app shell until answered. UUID generated on accept for anonymous_id.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/TelemetryConsentDialog.tsx

@@ -0,0 +1,68 @@
+import { ShieldCheck } from '@phosphor-icons/react'
+
+interface TelemetryConsentDialogProps {
+  onAccept: () => void
+  onDecline: () => void
+}
+
+export function TelemetryConsentDialog({ onAccept, onDecline }: TelemetryConsentDialogProps) {
+  return (
+    <div
+      className="fixed inset-0 flex items-center justify-center z-50"
+      style={{ background: 'rgba(0,0,0,0.4)' }}
+    >
+      <div
+        className="bg-background border border-border rounded-lg shadow-xl"
+        style={{ width: 440, padding: 32, display: 'flex', flexDirection: 'column', gap: 20, alignItems: 'center' }}
+      >
+        <ShieldCheck size={40} weight="duotone" style={{ color: 'var(--primary)' }} />
+
+        <div style={{ textAlign: 'center' }}>
+          <h2 style={{ fontSize: 18, fontWeight: 600, color: 'var(--foreground)', margin: 0 }}>
+            Help improve Laputa
+          </h2>
+          <p style={{ fontSize: 13, color: 'var(--muted-foreground)', lineHeight: 1.6, marginTop: 8 }}>
+            Send anonymous crash reports to help us fix bugs faster.
+            No vault content, no personal data, no tracking.
+          </p>
+        </div>
+
+        <div style={{ fontSize: 12, color: 'var(--muted-foreground)', lineHeight: 1.6, width: '100%' }}>
+          <p style={{ margin: '0 0 6px', fontWeight: 500, color: 'var(--foreground)' }}>What we collect:</p>
+          <ul style={{ margin: 0, paddingLeft: 18 }}>
+            <li>Stack traces from errors (JS &amp; Rust)</li>
+            <li>App version, OS, and architecture</li>
+          </ul>
+          <p style={{ margin: '10px 0 6px', fontWeight: 500, color: 'var(--foreground)' }}>What we never collect:</p>
+          <ul style={{ margin: 0, paddingLeft: 18 }}>
+            <li>No vault content, note titles, or file paths</li>
+            <li>No personal data or IP addresses</li>
+          </ul>
+        </div>
+
+        <div style={{ display: 'flex', gap: 12, width: '100%', marginTop: 4 }}>
+          <button
+            className="border border-border bg-transparent text-foreground rounded cursor-pointer hover:bg-accent"
+            style={{ flex: 1, fontSize: 13, padding: '10px 16px' }}
+            onClick={onDecline}
+            data-testid="telemetry-decline"
+          >
+            No thanks
+          </button>
+          <button
+            className="border-none rounded cursor-pointer"
+            style={{ flex: 1, fontSize: 13, padding: '10px 16px', background: 'var(--primary)', color: 'white', fontWeight: 500 }}
+            onClick={onAccept}
+            data-testid="telemetry-accept"
+          >
+            Allow anonymous reporting
+          </button>
+        </div>
+
+        <p style={{ fontSize: 11, color: 'var(--muted-foreground)', margin: 0, textAlign: 'center' }}>
+          You can change this anytime in Settings.
+        </p>
+      </div>
+    </div>
+  )
+}