Move Dockerfile and setup.sh out of .devcontainer folder

- Moved build files to goodmem-devcontainer root to hide from users
- Updated workflow paths to reference new locations
- Updated .gitignore to exclude Dockerfile and setup.sh from user workspaces
- Users only see .devcontainer/devcontainer.json in their workspace
- Version bumped to 0.4.8

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: mariamahmad8

src/goodmem-devcontainer/.devcontainer/Dockerfile

@@ -1,3 +1,3 @@
 # DevContainer internal files - users don't need these
-.devcontainer/Dockerfile
-.devcontainer/setup.sh
+Dockerfile
+setup.sh

src/goodmem-devcontainer/.devcontainer/setup.sh

@@ -1,6 +1,6 @@
 {
   "id": "goodmem-devcontainer",
-  "version": "0.4.7",
+  "version": "0.4.8",
   "name": "GoodMem DevContainer",
   "description": "Prebuilt devcontainer with full multi-language SDK setup for GoodMem projects.",
   "documentationURL": "https://github.com/PAIR-Systems-Inc/devcontainer",