feat: add Docker deployment, UAT test suites, and fix signup middleware bug

- Add Dockerfile, docker-entrypoint.sh, and .dockerignore for containerized deployment
- Fix middleware to exclude /api/tenants/signup from auth (P0 signup bug)
- Add Playwright E2E tests (16 browser tests) and curl-based API test script (80 tests)
- Add playwright config and dev dependency
- Update .gitignore with proper exclusions
- Add v1 milestone audit report and ISP system PRD

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

playwright.config.ts

@@ -0,0 +1,19 @@
+import { defineConfig } from "@playwright/test";
+
+export default defineConfig({
+  testDir: "./e2e",
+  timeout: 30000,
+  retries: 0,
+  use: {
+    baseURL: "http://localhost:3000",
+    headless: true,
+    screenshot: "only-on-failure",
+    trace: "on-first-retry",
+  },
+  projects: [
+    {
+      name: "chromium",
+      use: { browserName: "chromium" },
+    },
+  ],
+});