Scaffold project foundation

Fresh start: Vite + React 19 + strict TS, Tailwind v4, PWA, Vitest/Playwright.
Replaces the prior DeepSeek-built app (deleted; ~135 documented bugs, no VCS).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,13 @@
+node_modules
+dist
+dev-dist
+*.local
+.DS_Store
+playwright-report
+test-results
+.vite
+
+# Editor
+.vscode/*
+!.vscode/extensions.json
+.idea