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-tauri/src/commands/settings_commands.rs

@@ -0,0 +1,16 @@
+use crate::storage::secure;
+
+#[tauri::command]
+pub async fn set_api_key(key: String) -> Result<(), String> {
+    secure::store_api_key(&key)
+}
+
+#[tauri::command]
+pub async fn has_api_key() -> Result<bool, String> {
+    secure::has_api_key()
+}
+
+#[tauri::command]
+pub async fn delete_api_key() -> Result<(), String> {
+    secure::delete_api_key()
+}