feat(utils): 📦 Move sqlx-cli and mermaid-cli to terminal utilities

Add sqlx-cli and mermaid-cli to terminal-utils.nix while removing them
from
utils.nix to consolidate database and diagramming tools in the
appropriate
utility category.

- Move sqlx-cli (database migrations) to terminal utilities
- Move mermaid-cli (diagram generation) to terminal utilities
- Remove commented git-secrets from terminal utilities

This reorganization groups related development tools together for better
maintainability and logical organization of utility packages.

nixos/terminal-utils.nix

@@ -9,10 +9,12 @@
     git
     lazygit
     delta
+    sqlx-cli
+    mermaid-cli
     license-generator
     git-ignore
     gitleaks
-    git-secrets
+    # git-secrets
     pass-git-helper
     jujutsu
     jjui