feat(FN-3806): implement rooms create modal and chat sidebar with plugin ro

Adds a rooms feature to the chat sidebar including a new CreateRoomModal for creating chat rooms, with mobile selection handling and search empty-state copy fixes. Also introduces listTasksModifiedSince plugin contract and report plugin scaffold, replacing the removed dashboard roadmap backend.

Fusion-Task-Id: FN-3806

packages/dashboard/app/components/CreateRoomModal.css

@@ -0,0 +1,104 @@
+.create-room-modal {
+  display: flex;
+  flex-direction: column;
+  gap: var(--space-md);
+}
+
+.create-room-modal-name-group {
+  margin-bottom: 0;
+}
+
+.create-room-modal-name-field {
+  display: flex;
+  align-items: center;
+  gap: var(--space-sm);
+}
+
+.create-room-modal-name-hash {
+  color: var(--text-muted);
+  font-family: var(--font-mono);
+}
+
+.create-room-modal-name-field .input {
+  flex: 1;
+}
+
+.create-room-modal-selected {
+  display: flex;
+  flex-wrap: wrap;
+  gap: var(--space-sm);
+  padding: 0 var(--space-xl);
+}
+
+.create-room-modal-chip {
+  border-color: var(--border);
+}
+
+.create-room-modal-member-list {
+  display: flex;
+  flex-direction: column;
+  gap: var(--space-xs);
+  max-height: calc(var(--space-2xl) * 8);
+  overflow-y: auto;
+  padding: 0 var(--space-xl);
+}
+
+.create-room-modal-member-row {
+  display: flex;
+  align-items: center;
+  gap: var(--space-sm);
+  text-align: left;
+  border: 1px solid var(--border);
+  border-radius: var(--radius-md);
+  padding: var(--space-sm);
+  background: var(--surface);
+  color: var(--text);
+  transition: background var(--transition-fast), border-color var(--transition-fast);
+}
+
+.create-room-modal-member-row:hover {
+  background: var(--card-hover);
+}
+
+.create-room-modal-member-row:focus-visible {
+  outline: none;
+  box-shadow: var(--focus-ring-strong);
+}
+
+.create-room-modal-member-row--selected {
+  border-color: var(--todo);
+  background: color-mix(in srgb, var(--todo) 12%, transparent);
+}
+
+.create-room-modal-member-role {
+  margin-left: auto;
+  color: var(--text-muted);
+  font-size: var(--space-sm);
+}
+
+.create-room-modal-empty {
+  color: var(--text-muted);
+  padding: var(--space-md);
+  text-align: center;
+}
+
+@media (max-width: 768px) {
+  .create-room-modal {
+    width: 100%;
+  }
+
+  .create-room-modal-selected,
+  .create-room-modal-member-list {
+    padding: 0 var(--space-md);
+  }
+
+  .create-room-modal .modal-actions {
+    display: flex;
+    flex-direction: column;
+    gap: var(--space-sm);
+  }
+
+  .create-room-modal .modal-actions .btn {
+    width: 100%;
+  }
+}