feat(gtm): Implement Rich Session Browser UI

- Replaced the basic session list with a dedicated, card-based Session Browser page.
- Each session card now displays product name, category, description, and a thumbnail placeholder for better usability.
- Updated the backend DB manager to extract this rich information from the existing JSON data store.
- Refactored the frontend (App.tsx, types.ts) to support the new UI and data structure.
- Added new component SessionBrowser.tsx and its corresponding CSS.
- Updated documentation to reflect the v2.6 changes.

gtm-architect/components/SessionBrowser.css

@@ -0,0 +1,134 @@
+.session-browser {
+  padding: 20px;
+  background-color: #f0f2f5;
+  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
+}
+
+.session-browser h2 {
+  text-align: center;
+  color: #333;
+  margin-bottom: 24px;
+}
+
+.session-grid {
+  display: grid;
+  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
+  gap: 20px;
+}
+
+.session-card {
+  background-color: #ffffff;
+  border-radius: 12px;
+  box-shadow: 0 4px 12px rgba(0, 0, 0, 0.08);
+  overflow: hidden;
+  display: flex;
+  flex-direction: column;
+  transition: transform 0.2s ease-in-out, box-shadow 0.2s ease-in-out;
+}
+
+.session-card:hover {
+  transform: translateY(-5px);
+  box-shadow: 0 8px 20px rgba(0, 0, 0, 0.12);
+}
+
+.card-header {
+  padding: 16px;
+  display: flex;
+  align-items: center;
+  border-bottom: 1px solid #e8e8e8;
+}
+
+.category-icon {
+  font-size: 24px;
+  margin-right: 12px;
+}
+
+.card-header h3 {
+  margin: 0;
+  font-size: 1.1rem;
+  color: #1a1a1a;
+  white-space: nowrap;
+  overflow: hidden;
+  text-overflow: ellipsis;
+}
+
+.thumbnail-placeholder {
+  width: 100%;
+  height: 150px;
+  background-color: #e9ecef;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  color: #adb5bd;
+  font-size: 1.5rem;
+}
+
+.thumbnail-placeholder span {
+    font-size: 3rem;
+}
+
+.thumbnail-placeholder p {
+    margin-top: 8px;
+    font-size: 0.9rem;
+}
+
+.card-content {
+  padding: 16px;
+  flex-grow: 1; /* Ensures content area expands */
+}
+
+.product-description {
+  font-size: 0.9rem;
+  color: #555;
+  margin-bottom: 12px;
+  height: 4.5em; /* Approximately 3 lines of text */
+  overflow: hidden;
+  text-overflow: ellipsis;
+  display: -webkit-box;
+  -webkit-line-clamp: 3;
+  -webkit-box-orient: vertical;
+}
+
+.last-updated {
+  font-size: 0.8rem;
+  color: #888;
+  margin-top: auto; /* Pushes to the bottom if content is short */
+}
+
+.card-actions {
+  display: flex;
+  justify-content: space-between;
+  padding: 12px 16px;
+  border-top: 1px solid #e8e8e8;
+  background-color: #fafafa;
+}
+
+.card-actions button {
+  border: none;
+  border-radius: 6px;
+  padding: 8px 16px;
+  font-weight: 600;
+  cursor: pointer;
+  transition: background-color 0.2s, color 0.2s;
+}
+
+.load-btn {
+  background-color: #007bff;
+  color: white;
+}
+
+.load-btn:hover {
+  background-color: #0056b3;
+}
+
+.delete-btn {
+  background-color: #fceeee;
+  color: #d9534f;
+}
+
+.delete-btn:hover {
+  background-color: #f8d7da;
+  color: #b0413e;
+}
+