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/hooks/useDocker.ts

@@ -0,0 +1,61 @@
+import { useCallback } from "react";
+import { listen } from "@tauri-apps/api/event";
+import { useAppState } from "../store/appState";
+import * as commands from "../lib/tauri-commands";
+
+export function useDocker() {
+  const {
+    dockerAvailable,
+    setDockerAvailable,
+    imageExists,
+    setImageExists,
+  } = useAppState();
+
+  const checkDocker = useCallback(async () => {
+    try {
+      const available = await commands.checkDocker();
+      setDockerAvailable(available);
+      return available;
+    } catch {
+      setDockerAvailable(false);
+      return false;
+    }
+  }, [setDockerAvailable]);
+
+  const checkImage = useCallback(async () => {
+    try {
+      const exists = await commands.checkImageExists();
+      setImageExists(exists);
+      return exists;
+    } catch {
+      setImageExists(false);
+      return false;
+    }
+  }, [setImageExists]);
+
+  const buildImage = useCallback(
+    async (onProgress?: (msg: string) => void) => {
+      const unlisten = onProgress
+        ? await listen<string>("image-build-progress", (event) => {
+            onProgress(event.payload);
+          })
+        : null;
+
+      try {
+        await commands.buildImage();
+        setImageExists(true);
+      } finally {
+        unlisten?.();
+      }
+    },
+    [setImageExists],
+  );
+
+  return {
+    dockerAvailable,
+    imageExists,
+    checkDocker,
+    checkImage,
+    buildImage,
+  };
+}