Add Stripe embedded onboarding

- Update StripeConnectOnboarding component with embedded flow
- Add new Stripe routes and service methods for embedded onboarding
- Update EarningsStatus and EarningsDashboard to support new flow
- Add required frontend dependencies

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/routes/stripe.js

@@ -133,6 +133,41 @@ router.post("/account-links", authenticateToken, requireVerifiedEmail, async (re
   }
 });
 
+// Create account session for embedded onboarding
+router.post("/account-sessions", authenticateToken, requireVerifiedEmail, async (req, res, next) => {
+  let user = null;
+  try {
+    user = await User.findByPk(req.user.id);
+
+    if (!user || !user.stripeConnectedAccountId) {
+      return res.status(400).json({ error: "No connected account found" });
+    }
+
+    const accountSession = await StripeService.createAccountSession(
+      user.stripeConnectedAccountId
+    );
+
+    const reqLogger = logger.withRequestId(req.id);
+    reqLogger.info("Stripe account session created", {
+      userId: req.user.id,
+      stripeConnectedAccountId: user.stripeConnectedAccountId,
+    });
+
+    res.json({
+      clientSecret: accountSession.client_secret,
+    });
+  } catch (error) {
+    const reqLogger = logger.withRequestId(req.id);
+    reqLogger.error("Stripe account session creation failed", {
+      error: error.message,
+      stack: error.stack,
+      userId: req.user.id,
+      stripeConnectedAccountId: user?.stripeConnectedAccountId,
+    });
+    next(error);
+  }
+});
+
 // Get account status
 router.get("/account-status", authenticateToken, async (req, res, next) => {
   let user = null;