Initiële commit: VibeFinance 3-container opzet

Basislijn van de bestaande applicatie (Vite/React frontend, Express
backend, PostgreSQL) zoals die in de index stond, plus dev-, release-
en documentatiescripts.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

frontend/src/App.css

@@ -0,0 +1,28 @@
+*, *::before, *::after {
+  box-sizing: border-box;
+  margin: 0;
+  padding: 0;
+}
+
+html, body, #root {
+  height: 100%;
+  width: 100%;
+}
+
+input[type="number"]::-webkit-inner-spin-button {
+  opacity: 0.4;
+}
+
+.nav-tabs {
+  display: flex;
+  gap: 2px;
+  overflow-x: auto;
+}
+
+.nav-tabs::-webkit-scrollbar {
+  display: none;
+}
+
+@keyframes spin {
+  to { transform: rotate(360deg); }
+}