Add container registry pull, image source settings, and global AWS config

Support pulling images from registry (default: repo.anhonesthost.net/cybercovellc/triple-c/triple-c-sandbox:latest),
local builds, or custom images via a new settings UI. Add global AWS configuration
(config path auto-detect, profile picker, region) that serves as defaults overridable
per-project for Bedrock auth.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/src/hooks/useDocker.ts

@@ -51,11 +51,30 @@ export function useDocker() {
     [setImageExists],
   );
 
+  const pullImage = useCallback(
+    async (imageName: string, onProgress?: (msg: string) => void) => {
+      const unlisten = onProgress
+        ? await listen<string>("image-pull-progress", (event) => {
+            onProgress(event.payload);
+          })
+        : null;
+
+      try {
+        await commands.pullImage(imageName);
+        setImageExists(true);
+      } finally {
+        unlisten?.();
+      }
+    },
+    [setImageExists],
+  );
+
   return {
     dockerAvailable,
     imageExists,
     checkDocker,
     checkImage,
     buildImage,
+    pullImage,
   };
 }