feat: initial prototype works

I can log in and create a book! Woo!

api/src/app/routes/auth/index.ts

@@ -0,0 +1,85 @@
+import { FastifyPluginAsync } from "fastify";
+import { AuthService } from "../../services/auth.service";
+import { AuthResponse } from "@library/shared-types";
+
+const authRoutes: FastifyPluginAsync = async (app) => {
+  const authService = new AuthService(app);
+
+  /**
+   * Discord OAuth callback.
+   */
+  app.get("/callback", async (request, reply) => {
+    try {
+      const tokenResult = await app.oauth2Discord.getAccessTokenFromAuthorizationCodeFlow(
+        request
+      );
+
+      // Get user data from Discord API
+      const discordResponse = await fetch("https://discord.com/api/users/@me", {
+        headers: {
+          Authorization: `Bearer ${tokenResult.token.access_token}`,
+        },
+      });
+
+      if (!discordResponse.ok) {
+        throw new Error("Failed to fetch Discord user data");
+      }
+
+      const userData = await discordResponse.json();
+
+      // Create or update user in database
+      const user = await authService.createOrUpdateUserFromDiscord(userData);
+
+      // Generate JWT
+      const jwt = await authService.generateToken(user);
+
+      // Set cookie and redirect to frontend
+      reply
+        .setCookie("auth-token", jwt, {
+          path: "/",
+          httpOnly: true,
+          secure: process.env.NODE_ENV === "production",
+          sameSite: "lax",
+          maxAge: 7 * 24 * 60 * 60, // 7 days
+        })
+        .redirect("/"); // Redirect to root since API serves frontend
+    } catch (error) {
+      app.log.error({ err: error }, "Auth callback error");
+      reply
+        .code(401)
+        .send({ error: "Authentication failed", details: error instanceof Error ? error.message : String(error) });
+    }
+  });
+
+  /**
+   * Get current user.
+   */
+  app.get<{ Reply: AuthResponse | { error: string } }>(
+    "/me",
+    {
+      preValidation: [app.authenticate],
+    },
+    async (request) => {
+      const user = request.user as any;
+      const token = await authService.generateToken(user);
+
+      return {
+        user,
+        accessToken: token,
+      };
+    }
+  );
+
+  /**
+   * Logout.
+   */
+  app.post("/logout", async (request, reply) => {
+    reply
+      .clearCookie("auth-token", {
+        path: "/",
+      })
+      .send({ message: "Logged out successfully" });
+  });
+};
+
+export default authRoutes;