refactor: restructure project from bookmann to shelf

- Rename project from 'bookmann' to 'shelf'
- Move all backend/ contents to root level (flatten structure)
- Update Go module name from 'bookmann' to 'shelf'
- Update all import paths to use new 'shelf' module
- Update Dockerfile to work without backend/ subdirectory
- Update docker-compose.yml to use new structure and rename containers
- Update .gitignore for new file paths
- Update README.md with new project name and structure
- Regenerate database code with new module imports

docker-compose.yml

@@ -3,14 +3,14 @@ version: "3.8"
 services:
   db:
     image: postgres:15-alpine
-    container_name: bookmann_db
+    container_name: shelf_db
     environment:
       POSTGRES_DB: ebookdb
       POSTGRES_USER: postgres
       POSTGRES_PASSWORD: ${DBPASS}
     volumes:
       - postgres_data:/var/lib/postgresql/data
-      - ./backend/migrations:/docker-entrypoint-initdb.d
+      - ./migrations:/docker-entrypoint-initdb.d
     ports:
       - "5432:5432"
     healthcheck:
@@ -21,11 +21,11 @@ services:
     env_file:
       - .env
 
-  backend:
+  app:
     build:
       context: .
-      dockerfile: ./backend/Dockerfile
-    container_name: bookmann
+      dockerfile: ./Dockerfile
+    container_name: shelf
     environment:
       DATABASE_HOST: db
       DATABASE_PORT: 5432
@@ -40,7 +40,7 @@ services:
       db:
         condition: service_healthy
     volumes:
-      - ./backend/uploads:/app/uploads
+      - ./uploads:/app/uploads
     healthcheck:
       test: ["CMD", "curl", "-f", "http://localhost:8765/"]
       interval: 30s