Update project configuration for Bookhoard organization rename

Phase 1 of Gitea repository migration:
- Rename docker containers: bookmann_db → bookhoard_db, bookmann → bookhoard
- Update database name: bookmann → bookhoard
- Rename environment variables: BOOKMANN_* → BOOKHOARD_*
- Update documentation references to new project name

This prepares the codebase for migration to Bookhoard organization.

docker-compose.yml

@@ -3,9 +3,9 @@ version: "3.8"
 services:
   db:
     image: postgres:15-alpine
-    container_name: bookmann_db
+    container_name: bookhoard_db
     environment:
-      POSTGRES_DB: bookmann
+      POSTGRES_DB: bookhoard
       POSTGRES_USER: postgres
       POSTGRES_PASSWORD: ${DBPASS}
     volumes:
@@ -20,13 +20,13 @@ services:
     build:
       context: .
       dockerfile: ./Dockerfile
-    container_name: bookmann
+    container_name: bookhoard
     environment:
       DATABASE_HOST: db
       DATABASE_PORT: 5432
       DATABASE_USER: postgres
       DATABASE_PASSWORD: ${DBPASS}
-      DATABASE_NAME: bookmann
+      DATABASE_NAME: bookhoard
       JWT_SECRET: ${JWT_SECRET}
       SERVER_PORT: 8765
       TEST_MODE: ${TEST_MODE:-false}