feat: leads QR UX — merged confirm modes, faster scanning, correct capture identity

- Merge Rapid + Qualify scan modes into single Confirm mode with two-button card:
  "Add & Scan Next" (resets) and "Add & View Lead" (navigates to detail). Same
  two-button pattern on the reenable card: "Restore & Scan Next" / "Restore & View Lead".
  Stale 'qualify' localStorage values normalized to 'rapid' via $derived.by().
- QR scanner speed: fps 10→25, qrbox 82%→88%, useBarCodeDetectorIfSupported (native
  BarcodeDetector API on Chrome/Edge — significantly faster than ZXing JS fallback)
- Fix capture identity stored in external_person_id / group:
  licensed exhibit user → their email; shared passcode → 'shared_passcode' label
  (not the raw passcode); Aether user bypassing exhibit sign-in → access_type string
  ('trusted', 'manager', 'super', etc.). Consistent across all three lead capture
  components (single scanner, multi scanner, manual search).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/lib/elements/element_qr_scanner_v3.svelte

@@ -27,7 +27,7 @@
     let {
         start_qr_scanner = $bindable(true),
         on_qr_scan_result,
-        qr_fps = 10,
+        qr_fps = 25,
         qr_facing_mode = 'environment'
     }: Props = $props();
 
@@ -90,9 +90,14 @@
                     fps: qr_fps,
                     // Use a percentage of the viewfinder so it scales on any screen size
                     qrbox: (w: number, h: number) => {
-                        const side = Math.floor(Math.min(w, h) * 0.82);
+                        const side = Math.floor(Math.min(w, h) * 0.88);
                         return { width: side, height: side };
-                    }
+                    },
+                    // Use native BarcodeDetector API on Chrome/Edge — significantly faster
+                    // than the JS ZXing fallback used on Firefox/older Safari.
+                    // Cast: experimentalFeatures exists at runtime but is missing from the
+                    // html5-qrcode TypeScript type definitions for this version.
+                    ...({ experimentalFeatures: { useBarCodeDetectorIfSupported: true } } as { experimentalFeatures: { useBarCodeDetectorIfSupported: boolean } })
                 },
                 on_scan_success,
                 on_scan_error