fix: 修复JWT密钥配置和容器内配置文件路径问题

- 修复YAML配置文件字段格式错误（大写->小写）
- 修复JWT密钥未正确识别的问题
- 修复容器内配置文件路径问题，使用绝对路径/etc/photography-api.yaml
- 修复迁移工具配置文件路径
- 修复Dockerfile工作目录设置

解决了'field auth.access_secret is not set'的配置错误

backend/etc/photography-api.yaml

@@ -3,41 +3,41 @@ Host: 0.0.0.0
 Port: 8080
 
 # 数据库配置
-Database:
-  Driver: sqlite
-  FilePath: data/photography.db
-  Host: localhost
-  Port: 5432
-  Database: photography
-  Username: postgres
-  Password: ""
-  Charset: utf8mb4
-  SSLMode: disable
-  MaxOpenConns: 100
-  MaxIdleConns: 10
+database:
+  driver: sqlite
+  file_path: data/photography.db
+  host: localhost
+  port: 5432
+  database: photography
+  username: postgres
+  password: ""
+  charset: utf8mb4
+  ssl_mode: disable
+  max_open_conns: 100
+  max_idle_conns: 10
 
 # 认证配置
-Auth:
-  AccessSecret: photography-secret-key-2024
-  AccessExpire: 86400
+auth:
+  access_secret: photography-secret-key-2024
+  access_expire: 86400
 
 # 文件上传配置
-FileUpload:
-  MaxSize: 10485760  # 10MB
-  UploadDir: uploads
-  AllowedTypes:
+file_upload:
+  max_size: 10485760  # 10MB
+  upload_dir: uploads
+  allowed_types:
     - image/jpeg
     - image/png
     - image/gif
     - image/webp
 
 # 中间件配置
-Middleware:
-  EnableCORS: true
-  EnableLogger: true
-  EnableErrorHandle: true
-  CORSOrigins:
+middleware:
+  enable_cors: true
+  enable_logger: true
+  enable_error_handle: true
+  cors_origins:
     - http://localhost:3000
     - http://localhost:3001
     - http://localhost:5173
-  LogLevel: info
+  log_level: info