feat(frontend): add React chat UI with SSE parsing and source accordion

frontend/src/api.ts

@@ -0,0 +1,86 @@
+import { parseSSE, type SSEEvent } from "./lib/sse";
+
+export interface Source {
+  reference: string;
+  text: string;
+  book: string;
+  chapter: number;
+  verse: number;
+  page: number;
+  file: string;
+  score: number;
+}
+
+export interface Status {
+  state: "ready" | "indexing" | "error";
+  pdfs_total: number;
+  pdfs_indexed: number;
+  chunks: number;
+  model: string;
+  last_indexed_at: string | null;
+  errors: string[];
+}
+
+export interface ChatMessage {
+  role: "user" | "assistant";
+  content: string;
+}
+
+const API_BASE = import.meta.env.VITE_API_BASE_URL ?? "";
+
+async function request<T>(path: string, init?: RequestInit): Promise<T> {
+  const response = await fetch(`${API_BASE}${path}`, {
+    headers: { "Content-Type": "application/json" },
+    ...init,
+  });
+
+  if (!response.ok) {
+    let detail = `Erro ${response.status}`;
+    try {
+      const body = (await response.json()) as { detail?: string };
+      if (body.detail) {
+        detail = body.detail;
+      }
+    } catch {
+      /* resposta sem corpo JSON */
+    }
+    throw new Error(detail);
+  }
+
+  return (await response.json()) as T;
+}
+
+export function fetchStatus(): Promise<Status> {
+  return request<Status>("/api/status");
+}
+
+export function reindex(): Promise<{ state: string }> {
+  return request<{ state: string }>("/api/reindex", { method: "POST" });
+}
+
+/** Envia a mensagem e devolve os eventos do stream. */
+export async function* sendMessage(
+  message: string,
+  history: ChatMessage[],
+): AsyncGenerator<SSEEvent> {
+  const response = await fetch(`${API_BASE}/api/chat`, {
+    method: "POST",
+    headers: { "Content-Type": "application/json" },
+    body: JSON.stringify({ message, history }),
+  });
+
+  if (!response.ok || !response.body) {
+    let detail = `Erro ${response.status}`;
+    try {
+      const body = (await response.json()) as { detail?: string };
+      if (body.detail) {
+        detail = body.detail;
+      }
+    } catch {
+      /* resposta sem corpo JSON */
+    }
+    throw new Error(detail);
+  }
+
+  yield* parseSSE(response.body);
+}