Add Chrome extension cookie bridge for session import

Users logged into Alta in Chrome can now send their session cookie
to the running Electron app via a local HTTP server on port 18247,
eliminating the need for re-authentication.

- main.js: HTTP cookie server with CORS, token, domain validation
- preload.js: onExtensionCookie push-pattern IPC bridge
- renderer.js: handleExtensionCookie sets session, fetches devices
- chrome-extension/: Manifest V3 extension with popup UI
- CLAUDE.md: updated architecture docs

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

chrome-extension/popup.css

@@ -0,0 +1,100 @@
+/* Dark theme matching the Electron app */
+body {
+  margin: 0;
+  padding: 0;
+  font-family: 'Segoe UI', -apple-system, BlinkMacSystemFont, Roboto, sans-serif;
+  background: #1E1E1E;
+  color: #E0E0E0;
+  font-size: 14px;
+  min-width: 300px;
+}
+
+.popup-container {
+  padding: 16px;
+}
+
+h1 {
+  font-size: 16px;
+  font-weight: 600;
+  color: #0E7AFE;
+  margin: 0 0 12px 0;
+  text-align: center;
+  text-transform: uppercase;
+  letter-spacing: 0.5px;
+}
+
+.tab-info {
+  background: #2D2D30;
+  border: 1px solid #3C3C3C;
+  border-radius: 4px;
+  padding: 10px 12px;
+  margin-bottom: 12px;
+  font-size: 13px;
+  color: #999999;
+  word-break: break-all;
+}
+
+.tab-info.detected {
+  color: #4CAF50;
+  border-color: #4CAF50;
+}
+
+.tab-info.not-detected {
+  color: #F44336;
+  border-color: #F44336;
+}
+
+.send-btn {
+  display: block;
+  width: 100%;
+  padding: 10px 16px;
+  font-family: inherit;
+  font-size: 14px;
+  font-weight: bold;
+  color: white;
+  background: #0E7AFE;
+  border: none;
+  border-radius: 4px;
+  cursor: pointer;
+  transition: background 0.2s ease;
+}
+
+.send-btn:hover:not(:disabled) {
+  background: #0A5FD9;
+}
+
+.send-btn:disabled {
+  opacity: 0.5;
+  cursor: not-allowed;
+}
+
+.status-msg {
+  margin-top: 10px;
+  padding: 8px 12px;
+  border-radius: 4px;
+  font-size: 13px;
+  font-weight: bold;
+  display: none;
+  border: 1px solid transparent;
+}
+
+.status-msg.success {
+  display: block;
+  background: rgba(76, 175, 80, 0.1);
+  color: #4CAF50;
+  border-color: #4CAF50;
+}
+
+.status-msg.error {
+  display: block;
+  background: rgba(244, 67, 54, 0.1);
+  color: #F44336;
+  border-color: #F44336;
+}
+
+.status-msg.info {
+  display: block;
+  background: rgba(14, 122, 254, 0.1);
+  color: #0E7AFE;
+  border-color: #0E7AFE;
+}