Set up Go module and project structure

- Populated .gitignore with Go-specific patterns
- Created placeholder Go files with basic package structure:
  - bookstack.go: Client and Config setup
  - types.go: Data structures (Book, Page, Chapter, Shelf, SearchResult)
  - errors.go: Error handling types with sentinel errors
  - http.go: HTTP helper placeholder with ListOptions
  - books.go, pages.go, chapters.go, shelves.go, search.go: Service placeholders
- Verified build succeeds with go build ./...
- No external dependencies added (stdlib only)

All files compile successfully and follow flat package structure.

bookstack.go

@@ -0,0 +1,63 @@
+package bookstack
+
+import (
+	"net/http"
+	"time"
+)
+
+// Config holds configuration for the Bookstack API client.
+type Config struct {
+	// BaseURL is the base URL of the Bookstack instance (e.g., "https://docs.example.com")
+	BaseURL string
+
+	// TokenID is the Bookstack API token ID
+	TokenID string
+
+	// TokenSecret is the Bookstack API token secret
+	TokenSecret string
+
+	// HTTPClient is the HTTP client to use for requests.
+	// If nil, a default client with 30s timeout will be used.
+	HTTPClient *http.Client
+}
+
+// Client is the main Bookstack API client.
+type Client struct {
+	baseURL     string
+	tokenID     string
+	tokenSecret string
+	httpClient  *http.Client
+
+	// Service instances
+	Books    *BooksService
+	Pages    *PagesService
+	Chapters *ChaptersService
+	Shelves  *ShelvesService
+	Search   *SearchService
+}
+
+// NewClient creates a new Bookstack API client.
+func NewClient(cfg Config) *Client {
+	httpClient := cfg.HTTPClient
+	if httpClient == nil {
+		httpClient = &http.Client{
+			Timeout: 30 * time.Second,
+		}
+	}
+
+	c := &Client{
+		baseURL:     cfg.BaseURL,
+		tokenID:     cfg.TokenID,
+		tokenSecret: cfg.TokenSecret,
+		httpClient:  httpClient,
+	}
+
+	// Initialize services
+	c.Books = &BooksService{client: c}
+	c.Pages = &PagesService{client: c}
+	c.Chapters = &ChaptersService{client: c}
+	c.Shelves = &ShelvesService{client: c}
+	c.Search = &SearchService{client: c}
+
+	return c
+}