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/container_config.rs

@@ -0,0 +1,16 @@
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct ContainerInfo {
+    pub container_id: String,
+    pub project_id: String,
+    pub status: String,
+    pub image: String,
+}
+
+pub const IMAGE_NAME: &str = "triple-c";
+pub const IMAGE_TAG: &str = "latest";
+
+pub fn full_image_name() -> String {
+    format!("{IMAGE_NAME}:{IMAGE_TAG}")
+}