feat(startup): 服务端启动 bootstrap 与缓存预热

- 新增 STARTUP_BOOTSTRAP_ENABLED / STARTUP_CACHE_WARMUP_ENABLED 配置开关
- lifespan 拆分 bootstrap 步骤并后台线程预热缓存，失败可降级继续启动
- server_start.sh / web_start.sh 扩展 SERVER_PORT、启动与调度开关的 env 覆盖
- bootstrap_paddleocr_mobile.sh 改用 python3 并补充 poppler-utils 依赖
- 补充启动 bootstrap 与 env 覆盖优先级测试

server/src/app/core/config.py

@@ -43,6 +43,8 @@ class Settings(BaseSettings):
     app_port: int = Field(default=8000, alias="SERVER_PORT")
     server_workers: int = Field(default=1, alias="SERVER_WORKERS")
     web_concurrency: int | None = Field(default=None, alias="WEB_CONCURRENCY")
+    startup_bootstrap_enabled: bool = Field(default=True, alias="STARTUP_BOOTSTRAP_ENABLED")
+    startup_cache_warmup_enabled: bool = Field(default=False, alias="STARTUP_CACHE_WARMUP_ENABLED")
     background_schedulers_enabled: bool = Field(
         default=True,
         alias="BACKGROUND_SCHEDULERS_ENABLED",