chore: restructure project into backend and frontend folders

- Move all frontend code to frontend/ directory
- Add backend/ with Go project structure (cmd, internal, pkg)
- Add docker-compose.yml for orchestration

frontend/src/index.css

@@ -0,0 +1,34 @@
+@import "tailwindcss";
+
+@theme {
+  --color-primary: #1B263B;
+  --color-primary-container: #051125;
+  --color-tertiary: #F28C28;
+  --color-surface: #fbf8fb;
+  --color-surface-container: #f0edef;
+  --color-surface-container-low: #f5f3f5;
+  --color-surface-container-high: #eae7e9;
+  --color-on-surface: #1b1b1d;
+  --color-outline: #75777d;
+  --color-outline-variant: #c5c6cd;
+  --color-success: #16a34a;
+  --font-sans: 'Inter', system-ui, sans-serif;
+}
+
+* {
+  box-sizing: border-box;
+}
+
+body {
+  margin: 0;
+  font-family: var(--font-sans);
+  background-color: var(--color-surface);
+  color: var(--color-on-surface);
+  -webkit-font-smoothing: antialiased;
+  -moz-osx-font-smoothing: grayscale;
+}
+
+#root {
+  min-height: 100vh;
+  width: 100%;
+}