Initialize blog scaffold

Add the CLI, site, and sample content so the project can run locally.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

backend/internal/cli/markdown_test.go

@@ -0,0 +1,57 @@
+package cli
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+func TestReadWritePostFile(t *testing.T) {
+	dir := t.TempDir()
+	publishedAt := "2026-05-28T12:00:00+08:00"
+	post := postFile{
+		Path: filepath.Join(dir, "hello.md"),
+		Frontmatter: postFrontmatter{
+			ID:          "post-1",
+			Slug:        "hello",
+			Title:       "Hello",
+			Summary:     "Summary",
+			Status:      "published",
+			Tags:        []string{"go", "astro"},
+			Version:     2,
+			SlugSource:  "manual",
+			PublishedAt: &publishedAt,
+			CreatedAt:   "2026-05-28T11:00:00+08:00",
+			UpdatedAt:   "2026-05-28T12:00:00+08:00",
+		},
+		Body: "Body\n",
+	}
+
+	if err := writePostFile(post); err != nil {
+		t.Fatal(err)
+	}
+
+	got, err := readPostFile(post.Path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got.Frontmatter.ID != post.Frontmatter.ID || got.Frontmatter.Slug != post.Frontmatter.Slug {
+		t.Fatalf("frontmatter mismatch: %#v", got.Frontmatter)
+	}
+	if got.Body != post.Body {
+		t.Fatalf("body = %q, want %q", got.Body, post.Body)
+	}
+	if len(got.Frontmatter.Tags) != 2 || got.Frontmatter.Tags[1] != "astro" {
+		t.Fatalf("tags = %#v", got.Frontmatter.Tags)
+	}
+}
+
+func TestReadPostFileRequiresFrontmatter(t *testing.T) {
+	path := filepath.Join(t.TempDir(), "bad.md")
+	if err := os.WriteFile(path, []byte("no frontmatter"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := readPostFile(path); err == nil {
+		t.Fatal("expected frontmatter error")
+	}
+}