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/capabilities/default.json

@@ -0,0 +1,33 @@
+{
+  "identifier": "default",
+  "description": "Default capabilities for Triple-C",
+  "windows": ["main"],
+  "permissions": [
+    "core:default",
+    "core:event:default",
+    "core:event:allow-emit",
+    "core:event:allow-listen",
+    "core:event:allow-unlisten",
+    "core:event:allow-emit-to",
+    "dialog:default",
+    "dialog:allow-open",
+    "dialog:allow-save",
+    "dialog:allow-message",
+    "dialog:allow-ask",
+    "dialog:allow-confirm",
+    "store:default",
+    "store:allow-get",
+    "store:allow-set",
+    "store:allow-delete",
+    "store:allow-keys",
+    "store:allow-values",
+    "store:allow-entries",
+    "store:allow-length",
+    "store:allow-load",
+    "store:allow-reset",
+    "store:allow-save",
+    "store:allow-clear",
+    "opener:default",
+    "opener:allow-open-url"
+  ]
+}