refactor: convert to bun workspaces monorepo

- Move web app into apps/web/
- Create packages/shared/ with shared types
- Create plugins/decky-vault/ scaffold
- Root package.json manages workspaces only

apps/web/components/auth/__tests__/placeholder.test.tsx

@@ -0,0 +1,20 @@
+import { describe, it, expect } from "vitest"
+import fs from "node:fs"
+import path from "node:path"
+
+describe("auth form email placeholder text", () => {
+  it("all auth forms use you@deckyvault.xyz not you@example.com", () => {
+    const files = [
+      "components/auth/signup-form-step.tsx",
+      "components/auth/login-form.tsx",
+      "components/auth/forgot-password-form.tsx",
+    ]
+
+    for (const file of files) {
+      const fullPath = path.join(process.cwd(), file)
+      const content = fs.readFileSync(fullPath, "utf8")
+      expect(content).not.toContain('"you@example.com"')
+      expect(content).toContain('"you@deckyvault.xyz"')
+    }
+  })
+})