refactor: reorganize project structure and update configurations

- Move migrations/ to database/schema/ for clarity on database schema definitions
- Move sqlc.yaml to internal/database/ to group with database code
- Move static/ to cmd/server/static/ to co-locate with server
- Update all configuration files and documentation
- Follow Go project conventions for better organization

internal/handlers/auth.go

@@ -4,11 +4,14 @@ import (
 	"bookmann/internal/database"
 	"fmt"
 	"net/http"
+	"path/filepath"
+	"strings"
 	"time"
 
 	jwt "github.com/golang-jwt/jwt/v5"
 
 	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5"
 	"github.com/jackc/pgx/v5/pgtype"
 	"github.com/labstack/echo/v4"
 	"golang.org/x/crypto/bcrypt"
@@ -370,6 +373,31 @@ type AddEbookFolderRequest struct {
 	FolderPath string `json:"folder_path" validate:"required"`
 }
 
+// normalizePath cleans and normalizes folder paths for consistent storage and comparison
+func normalizePath(path string) string {
+	fmt.Printf("normalizePath input: '%s'\n", path)
+
+	var cleaned string
+	// Handle home directory expansion (~)
+	if strings.HasPrefix(path, "~/") {
+		// Keep the original path for ~ to preserve user's formatting
+		// Just normalize separators and that's it
+		cleaned = strings.ReplaceAll(path, "\\", "/")
+	} else {
+		// Clean the path to remove redundant separators, ., .. etc.
+		cleaned = filepath.Clean(path)
+		// Convert to consistent path separators (use forward slashes for storage)
+		cleaned = strings.ReplaceAll(cleaned, "\\", "/")
+		// Remove trailing slash unless it's root path
+		if len(cleaned) > 1 && strings.HasSuffix(cleaned, "/") {
+			cleaned = strings.TrimSuffix(cleaned, "/")
+		}
+	}
+
+	fmt.Printf("normalizePath output: '%s'\n", cleaned)
+	return cleaned
+}
+
 type EbookFolderResponse struct {
 	ID         string `json:"id"`
 	UserID     string `json:"user_id"`
@@ -397,9 +425,12 @@ func (h *AuthHandler) AddEbookFolder(c echo.Context) error {
 		return c.JSON(http.StatusBadRequest, map[string]string{"error": err.Error()})
 	}
 
+	// Normalize the folder path before storing
+	normalizedPath := normalizePath(req.FolderPath)
+
 	folder, err := h.db.AddUserEbookFolder(c.Request().Context(), database.AddUserEbookFolderParams{
 		UserID:     pgtype.UUID{Bytes: userUUID, Valid: true},
-		FolderPath: req.FolderPath,
+		FolderPath: normalizedPath,
 	})
 	if err != nil {
 		return c.JSON(http.StatusInternalServerError, map[string]string{"error": err.Error()})
@@ -426,6 +457,12 @@ func (h *AuthHandler) GetEbookFolders(c echo.Context) error {
 		return c.JSON(http.StatusInternalServerError, map[string]string{"error": err.Error()})
 	}
 
+	fmt.Printf("GetEbookFolders: user_id='%s'\n", userID)
+	for _, folder := range folders {
+		fmt.Printf("  Folder in DB: id='%s', path='%s'\n",
+			uuid.UUID(folder.ID.Bytes).String(), folder.FolderPath)
+	}
+
 	var response []EbookFolderResponse
 	for _, folder := range folders {
 		response = append(response, EbookFolderResponse{
@@ -455,14 +492,26 @@ func (h *AuthHandler) DeleteEbookFolder(c echo.Context) error {
 		return c.JSON(http.StatusBadRequest, map[string]string{"error": err.Error()})
 	}
 
-	err = h.db.DeleteUserEbookFolder(c.Request().Context(), database.DeleteUserEbookFolderParams{
+	// Normalize the folder path before deletion
+	normalizedPath := normalizePath(req.FolderPath)
+
+	// Debug logging - remove in production
+	fmt.Printf("DeleteEbookFolder: original path='%s', normalized path='%s', user_id='%s'\n",
+		req.FolderPath, normalizedPath, userID)
+
+	deletedFolder, err := h.db.DeleteUserEbookFolder(c.Request().Context(), database.DeleteUserEbookFolderParams{
 		UserID:     pgtype.UUID{Bytes: userUUID, Valid: true},
-		FolderPath: req.FolderPath,
+		FolderPath: normalizedPath,
 	})
 	if err != nil {
+		fmt.Printf("DeleteEbookFolder failed: %v\n", err)
+		if err == pgx.ErrNoRows {
+			return c.JSON(http.StatusNotFound, map[string]string{"error": "ebook folder not found"})
+		}
 		return c.JSON(http.StatusInternalServerError, map[string]string{"error": err.Error()})
 	}
 
+	fmt.Printf("DeleteEbookFolder succeeded: deleted folder with path '%s'\n", deletedFolder.FolderPath)
 	return c.JSON(http.StatusOK, map[string]string{"message": "ebook folder deleted successfully"})
 }