feat(bookstack-api-02m): create example code in examples/ directory

Add three example programs: basic (list books, get page), search
(full-text search with CLI args), and export (markdown/PDF export).

examples/basic/main.go

@@ -0,0 +1,59 @@
+// Basic example: set up client, list books, get a page.
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"os"
+
+	bookstack "code.beautifulmachines.dev/jakoubek/bookstack-api"
+)
+
+func main() {
+	client, err := bookstack.NewClient(bookstack.Config{
+		BaseURL:     os.Getenv("BOOKSTACK_URL"),
+		TokenID:     os.Getenv("BOOKSTACK_TOKEN_ID"),
+		TokenSecret: os.Getenv("BOOKSTACK_TOKEN_SECRET"),
+	})
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	ctx := context.Background()
+
+	// List first 5 books
+	books, err := client.Books.List(ctx, &bookstack.ListOptions{Count: 5})
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	for _, book := range books {
+		fmt.Printf("Book %d: %s\n", book.ID, book.Name)
+	}
+
+	// Get the first page if any books exist
+	if len(books) > 0 {
+		pages, err := client.Pages.List(ctx, &bookstack.ListOptions{
+			Count:  1,
+			Filter: map[string]string{"book_id": fmt.Sprintf("%d", books[0].ID)},
+		})
+		if err != nil {
+			log.Fatal(err)
+		}
+		if len(pages) > 0 {
+			page, err := client.Pages.Get(ctx, pages[0].ID)
+			if err != nil {
+				log.Fatal(err)
+			}
+			fmt.Printf("\nPage: %s\n%s\n", page.Name, page.HTML[:min(200, len(page.HTML))])
+		}
+	}
+}
+
+func min(a, b int) int {
+	if a < b {
+		return a
+	}
+	return b
+}