Redact personal data before publishing as public repo

- config/git/gitconfig: replace real name, email, SSH signing key, and
  self-hosted git credential URL with placeholder values

- stages/06-scripts.sh: remove hardcoded personal email from bw login;
  CLI prompts interactively

- config/shell/zshrc.local.example: replace personal server URLs
  (Nextcloud, LiteLLM proxy), university email address, institution-
  specific Canvas LMS URL, and identifying Canvas key prefix with
  generic example.com placeholders

- TODO.md: replace personal email and Nextcloud URL in code examples
  with generic placeholders

- stages/07-uv-projects.sh: remove private org name from comment

config/git/gitconfig

@@ -1,11 +1,9 @@
 [user]
-	name = Julian Prester
-	email = hi@julianprester.com
-	signingkey = ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIO14cVPAkygA4OIMmQ1PiBBQ9mQ+nY5n7XKJA0jD9ZOl github@julianprester.com
+	name = Your Name
+	email = your@email.com
+	# signingkey = <paste your SSH public key here, e.g. output of: cat ~/.ssh/id_ed25519.pub>
 [init]
 	defaultBranch = main
-[credential "https://git.julianprester.com"]
-	provider = generic
 [core]
 	compression = 0
 	excludesfile = ~/.gitignore