Emdash source with visual editor image upload fix

Fixes:
1. media.ts: wrap placeholder generation in try-catch
2. toolbar.ts: check r.ok, display error message in popover

packages/core/tests/unit/api/email-settings-route.test.ts

@@ -0,0 +1,22 @@
+/**
+ * Email Settings Route Registration Test
+ *
+ * Regression test for https://github.com/emdash-cms/emdash/issues/151
+ * The email settings API route file existed but was never registered
+ * via injectRoute(), causing the endpoint to return 404.
+ */
+
+import { describe, expect, it, vi } from "vitest";
+
+import { injectCoreRoutes } from "../../../src/astro/integration/routes.js";
+
+describe("email settings route registration (#151)", () => {
+	it("registers /_emdash/api/settings/email route", () => {
+		const injectRoute = vi.fn();
+
+		injectCoreRoutes(injectRoute);
+
+		const patterns = injectRoute.mock.calls.map((call) => (call[0] as { pattern: string }).pattern);
+		expect(patterns).toContain("/_emdash/api/settings/email");
+	});
+});