feat: implement auth, projects, and frontend foundation

apps/web/src/state/auth.tsx

@@ -0,0 +1,63 @@
+import { createContext, useCallback, useContext, useEffect, useMemo, useState } from "react";
+
+import { apiClient } from "../api/client";
+import type { SessionPayload, SessionUser } from "../types";
+
+type AuthState = "loading" | "authenticated" | "unauthenticated";
+
+type AuthContextValue = {
+  state: AuthState;
+  user: SessionUser | null;
+  refreshSession: () => Promise<void>;
+  logout: () => Promise<void>;
+};
+
+const AuthContext = createContext<AuthContextValue | undefined>(undefined);
+
+export const AuthProvider = ({ children }: { children: React.ReactNode }) => {
+  const [state, setState] = useState<AuthState>("loading");
+  const [user, setUser] = useState<SessionUser | null>(null);
+
+  const refreshSession = useCallback(async () => {
+    setState("loading");
+    try {
+      const response = await apiClient.get<SessionPayload>("/auth/me");
+      setUser(response.data.user);
+      setState("authenticated");
+    } catch {
+      setUser(null);
+      setState("unauthenticated");
+    }
+  }, []);
+
+  const logout = useCallback(async () => {
+    await apiClient.post("/auth/logout");
+    setUser(null);
+    setState("unauthenticated");
+  }, []);
+
+  useEffect(() => {
+    void refreshSession();
+  }, [refreshSession]);
+
+  const value = useMemo(
+    () => ({
+      state,
+      user,
+      refreshSession,
+      logout
+    }),
+    [refreshSession, state, user, logout]
+  );
+
+  return <AuthContext.Provider value={value}>{children}</AuthContext.Provider>;
+};
+
+export const useAuth = (): AuthContextValue => {
+  const context = useContext(AuthContext);
+  if (!context) {
+    throw new Error("useAuth must be used within AuthProvider");
+  }
+
+  return context;
+};