Add git-crypt encryption for secrets.md and config.asp

Sensitive files are now encrypted at rest in the repo, allowing them
to be committed safely and synced between machines.

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

.gitattributes

@@ -0,0 +1,2 @@
+secrets.md filter=git-crypt diff=git-crypt
+includes/config.asp filter=git-crypt diff=git-crypt

.gitignore

@@ -1,6 +1,4 @@
-# Secrets
-secrets.md
-includes/config.asp
+# Secrets (encrypted by git-crypt)
 
 # Logs
 logs/