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/models/app_settings.rs

@@ -0,0 +1,20 @@
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct AppSettings {
+    pub default_ssh_key_path: Option<String>,
+    pub default_git_user_name: Option<String>,
+    pub default_git_user_email: Option<String>,
+    pub docker_socket_path: Option<String>,
+}
+
+impl Default for AppSettings {
+    fn default() -> Self {
+        Self {
+            default_ssh_key_path: None,
+            default_git_user_name: None,
+            default_git_user_email: None,
+            docker_socket_path: None,
+        }
+    }
+}