Remove outdated documentation files

- Deleted `I18N_IMPLEMENTATION_PLAN.md` and `PROJECT_PROGRESS.md` to declutter the repository.
- These documents were finalized, no longer relevant, and superseded by implemented features and external references.

docs/images/.gitkeep

@@ -0,0 +1,7 @@
+# Placeholder to keep this directory in git
+# Add your screenshots here:
+# - landing.png
+# - login.png
+# - admin-dashboard.png
+# - settings.png
+# - design-system.png