Add lightweight self-hosted Hugo CMS with GitHub API backend

Implements a Go-based CMS for editing Hugo posts and uploading images
via the GitHub REST API, with no database and Git as the source of truth.

Features:
- Single admin auth with bcrypt password and signed session cookies
- Dashboard, post listing with search, create/edit with EasyMDE editor
- Media library for static/uploads/ with drag-drop and clipboard paste
- Client-side autosave, unsaved changes warning, dark mode, responsive UI
- Modular packages for auth, github, posts, media, session, and handlers

Co-authored-by: codegirl007 <s.raide@gmail.com>

cms/Makefile

@@ -0,0 +1,16 @@
+.PHONY: build run test hash clean
+
+build:
+	go build -o hugo-cms ./cmd/server
+
+run:
+	go run ./cmd/server
+
+test:
+	go test ./...
+
+hash:
+	@read -p "Password: " pwd && go run ./cmd/hashpassword "$$pwd"
+
+clean:
+	rm -f hugo-cms