Add SSH key backup script and fix git config

- Copy actual .gitconfig instead of placeholder
- Create encrypted SSH key backup script with GPG
- Add SSH-based remote setup script
- Include restore instructions and security notes

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

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

.gitconfig

@@ -0,0 +1,14 @@
+# This is Git's per-user configuration file.
+[user]
+	name = David F Glidden
+	email = d@davidglidden.eu
+# Please adapt and uncomment the following lines:
+#	name = David GLIDDEN
+#	email = davidglidden@Macintosh.home
+[filter "lfs"]
+	clean = git-lfs clean -- %f
+	smudge = git-lfs smudge -- %f
+	process = git-lfs filter-process
+	required = true
+[url "git@github.com:"]
+	insteadOf = https://github.com/