Fix viewer share links to use LAN IP; bind Flask to 0.0.0.0

Share links copied from the Share modal were built with
window.location.origin, producing 127.0.0.1 URLs that remote
viewers could never reach.

- Bind Flask to 0.0.0.0 in gdpr_scanner.py (--host default),
  m365_launcher.py, and build_gdpr.py so the server is reachable
  on the local network. Internal loopback URLs (urllib exports,
  webview window, port probe) intentionally keep 127.0.0.1.
- Add /api/local_ip endpoint: UDP probe to 8.8.8.8 discovers the
  active LAN IP without sending real traffic.
- Add _getShareBaseUrl() in viewer.js: fetches /api/local_ip and
  substitutes the LAN IP; falls back to window.location.origin.
- createShareLink and copyTokenLink are now async and await
  _getShareBaseUrl() before building the viewer URL.
- Update CLAUDE.md and static/js/CLAUDE.md with the new invariants.

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

static/js/viewer.js

@@ -1,6 +1,20 @@
 // ── Viewer token management (#33) ─────────────────────────────────────────────
 // Share button → modal to create, copy, and revoke read-only viewer links.
 
+async function _getShareBaseUrl() {
+  // Use the machine's LAN IP so links work for remote users, not just localhost.
+  try {
+    const r = await fetch('/api/local_ip');
+    if (r.ok) {
+      const d = await r.json();
+      if (d.ip && d.ip !== '127.0.0.1') {
+        return 'http://' + d.ip + ':' + window.location.port;
+      }
+    }
+  } catch(e) {}
+  return window.location.origin;
+}
+
 function openShareModal() {
   document.getElementById('shareBackdrop').classList.add('open');
   document.getElementById('shareNewLinkRow').style.display = 'none';
@@ -69,7 +83,7 @@ async function createShareLink() {
     });
     if (!r.ok) throw new Error('Server error ' + r.status);
     const entry = await r.json();
-    const url = window.location.origin + '/view?token=' + encodeURIComponent(entry.token);
+    const url = (await _getShareBaseUrl()) + '/view?token=' + encodeURIComponent(entry.token);
     const urlInput = document.getElementById('shareNewLinkUrl');
     urlInput.value = url;
     document.getElementById('shareNewLinkRow').style.display = 'block';
@@ -86,8 +100,8 @@ function copyShareLink() {
   _copyText(url, document.getElementById('shareCopyBtn'));
 }
 
-function copyTokenLink(token, btn) {
-  const url = window.location.origin + '/view?token=' + encodeURIComponent(token);
+async function copyTokenLink(token, btn) {
+  const url = (await _getShareBaseUrl()) + '/view?token=' + encodeURIComponent(token);
   _copyText(url, btn);
 }