feat(web/ui): unify session opening and add repo card in project list

- Add openSession utility with tab deduplication/focus
- Use openSession in navbar live sessions, use-instance-actions, and project tool links
- Pass onAddRepository to ProjectListItem and add dashed 'Add Repository' card
- Style add-repo card in projects.css

apps/web/src/styles/pages/projects.css

@@ -177,8 +177,28 @@
 	color: var(--danger);
 }
 
-.project-add-repo {
-	display: none;
+.project-add-repo-card {
+	display: flex;
+	align-items: center;
+	justify-content: center;
+	gap: var(--space-3);
+	background: transparent;
+	color: var(--muted);
+	border-style: dashed;
+	cursor: pointer;
+	min-height: 120px;
+}
+
+.project-add-repo-card:hover {
+	background: var(--bg);
+	color: var(--ink);
+	border-color: var(--brand);
+}
+
+.project-add-repo-card .project-repo-name {
+	font-weight: 500;
+	white-space: normal;
+	text-align: center;
 }
 
 @media (max-width: 767px) {