feat: initial elysium idle game prototype

Sets up the full monorepo with pnpm workspaces. Includes shared types
package, Hono API with Discord OAuth/JWT auth, Prisma v6 + MongoDB
Atlas, and React + Vite frontend with game loop, five tabs, and
Discord-linked save/load.

apps/api/src/routes/auth.ts

@@ -0,0 +1,97 @@
+import type { Player } from "@elysium/types";
+import { Hono } from "hono";
+import { prisma } from "../db/client.js";
+import { INITIAL_GAME_STATE } from "../data/initialState.js";
+import {
+  buildOAuthUrl,
+  exchangeCode,
+  fetchDiscordUser,
+} from "../services/discord.js";
+import { signToken } from "../services/jwt.js";
+
+export const authRouter = new Hono();
+
+authRouter.get("/url", (context) => {
+  try {
+    const url = buildOAuthUrl();
+    return context.json({ url });
+  } catch {
+    return context.json({ error: "Failed to build OAuth URL" }, 500);
+  }
+});
+
+authRouter.get("/callback", async (context) => {
+  const code = context.req.query("code");
+
+  if (!code) {
+    return context.json({ error: "Missing code parameter" }, 400);
+  }
+
+  try {
+    const tokenData = await exchangeCode(code);
+    const discordUser = await fetchDiscordUser(tokenData.access_token);
+
+    const existing = await prisma.player.findUnique({
+      where: { discordId: discordUser.id },
+    });
+
+    const now = Date.now();
+
+    if (!existing) {
+      const player = await prisma.player.create({
+        data: {
+          discordId: discordUser.id,
+          username: discordUser.username,
+          discriminator: discordUser.discriminator,
+          avatar: discordUser.avatar,
+          characterName: discordUser.username,
+          createdAt: now,
+          lastSavedAt: now,
+          totalGoldEarned: 0,
+          totalClicks: 0,
+        },
+      });
+
+      const playerShape: Player = {
+        discordId: player.discordId,
+        username: player.username,
+        discriminator: player.discriminator,
+        avatar: player.avatar ?? null,
+        characterName: player.characterName,
+        createdAt: player.createdAt,
+        lastSavedAt: player.lastSavedAt,
+        totalGoldEarned: player.totalGoldEarned,
+        totalClicks: player.totalClicks,
+      };
+
+      const initialState = INITIAL_GAME_STATE(playerShape, playerShape.characterName);
+      await prisma.gameState.create({
+        data: {
+          discordId: player.discordId,
+          state: initialState,
+          updatedAt: now,
+        },
+      });
+
+      const jwtToken = signToken(player.discordId);
+      const clientUrl = process.env["CORS_ORIGIN"] ?? "http://localhost:5173";
+      return context.redirect(`${clientUrl}/auth/callback?token=${jwtToken}&isNew=true`);
+    }
+
+    const updated = await prisma.player.update({
+      where: { discordId: discordUser.id },
+      data: {
+        username: discordUser.username,
+        discriminator: discordUser.discriminator,
+        avatar: discordUser.avatar,
+      },
+    });
+
+    const jwtToken = signToken(updated.discordId);
+    const clientUrl = process.env["CORS_ORIGIN"] ?? "http://localhost:5173";
+    return context.redirect(`${clientUrl}/auth/callback?token=${jwtToken}&isNew=false`);
+  } catch {
+    const clientUrl = process.env["CORS_ORIGIN"] ?? "http://localhost:5173";
+    return context.redirect(`${clientUrl}/auth/callback?error=auth_failed`);
+  }
+});