Initial commit: Triple-C app, container, and CI

Tauri v2 desktop app (React/TypeScript + Rust) for managing
containerized Claude Code environments. Includes Gitea Actions
workflow for building and pushing the sandbox container image,
and a BUILDING.md guide for manual app builds on Linux and Windows.

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

app/src/index.css

@@ -0,0 +1,52 @@
+@import "tailwindcss";
+
+:root {
+  --bg-primary: #0d1117;
+  --bg-secondary: #161b22;
+  --bg-tertiary: #21262d;
+  --border-color: #30363d;
+  --text-primary: #e6edf3;
+  --text-secondary: #8b949e;
+  --accent: #58a6ff;
+  --accent-hover: #79c0ff;
+  --success: #3fb950;
+  --warning: #d29922;
+  --error: #f85149;
+}
+
+* {
+  margin: 0;
+  padding: 0;
+  box-sizing: border-box;
+}
+
+html, body, #root {
+  height: 100%;
+  width: 100%;
+  overflow: hidden;
+}
+
+body {
+  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
+  background-color: var(--bg-primary);
+  color: var(--text-primary);
+}
+
+/* Scrollbar styling */
+::-webkit-scrollbar {
+  width: 8px;
+  height: 8px;
+}
+
+::-webkit-scrollbar-track {
+  background: var(--bg-primary);
+}
+
+::-webkit-scrollbar-thumb {
+  background: var(--bg-tertiary);
+  border-radius: 4px;
+}
+
+::-webkit-scrollbar-thumb:hover {
+  background: var(--border-color);
+}