chore: remove examples/ from git tracking, add to .gitignore

The examples/ directory contains sample images used for manual testing only
and should not be versioned. Added rule to CLAUDE.md.

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

.gitignore

@@ -1,3 +1,6 @@
+# Example/sample files (images, fixtures used for manual testing)
+examples/
+
 # Firebase credentials
 backend/firebase-credentials.json
 client/android/app/google-services.json

CLAUDE.md

@@ -5,6 +5,11 @@
 - All code comments must be written in **English**.
 - All git commit messages must be written in **English**.
 
+## What NOT to commit
+
+- The `examples/` directory — it contains sample images and fixtures used for manual
+  testing only. It is listed in `.gitignore` and must never be staged or committed.
+
 ## Localisation
 
 **Rule:** Every table that stores human-readable text must have a companion `{table}_translations`