feat(v2): add multiple extra features from the pdf slides

frontend/src/lib/api.js

@@ -18,6 +18,39 @@ export async function uploadImage(file) {
   return parseResponse(response);
 }
 
+export async function getOperations() {
+  const response = await fetch(`${API_BASE}/api/operations/`);
+  return parseResponse(response);
+}
+
+export async function listStates(sessionId) {
+  const response = await fetch(`${API_BASE}/api/sessions/${sessionId}/states/`);
+  return parseResponse(response);
+}
+
+export async function applyStateOperation(stateId, operation, params = {}) {
+  const response = await fetch(`${API_BASE}/api/states/${stateId}/operations/`, {
+    method: "POST",
+    headers: { "Content-Type": "application/json" },
+    body: JSON.stringify({ operation, params })
+  });
+  return parseResponse(response);
+}
+
+export async function combineStates(operation, stateIds, params = {}) {
+  const response = await fetch(`${API_BASE}/api/states/combine/`, {
+    method: "POST",
+    headers: { "Content-Type": "application/json" },
+    body: JSON.stringify({ operation, state_ids: stateIds, params })
+  });
+  return parseResponse(response);
+}
+
+export async function getStateHistogram(stateId) {
+  const response = await fetch(`${API_BASE}/api/states/${stateId}/histogram/`);
+  return parseResponse(response);
+}
+
 export async function processImage(sessionId, operation, params) {
   const response = await fetch(`${API_BASE}/api/process/`, {
     method: "POST",