fix(hub): download Feishu resources via bot-owned lark-cli

Agent tool downloads and trigger attachment staging both used the SDK
messageResource path, which fails closed for multi-MB teacher files and
did not share the bot-identity transport contract. Route every download
through Hub-owned createFeishuBotCli (secret via stdin, disposable HOME,
HUB_FEISHU_CLI_BIN), keep workspace containment on write, and inject the
adapter in trigger tests.

hub/deploy/install_service.sh

@@ -164,6 +164,7 @@ DATABASE_URL=
 HUB_SILO_ORGANIZATION_ID=
 HUB_SYSTEMD_UNIT=$SERVICE_UNIT
 CPH_BIN=$CPH_BIN_DEFAULT
+HUB_FEISHU_CLI_BIN=/usr/local/bin/lark-cli
 HOST=$HOST
 PORT=$PORT
 HUB_PROJECT_WORKSPACE_ROOT=$WORKSPACE_ROOT