fix: change file permissions from 777 to 755 for security improvements

[osmontero]

This pull request standardizes file and directory permissions across the codebase by changing chmod commands from 777 (full access for everyone) to 755 (full access for owner, read/execute for others). This improves security by reducing unnecessary write access for group and other users. The changes affect backend installation logic, update procedures, Dockerfile setup, and user-facing installation instructions.

Backend installation and update logic:

• Changed chmod arguments from 777 to 755 in agent/collectors/filebeat_amd64.go, agent/updates/dependencies.go, and agent/updates/update.go to restrict permissions when installing or updating files and services. [1] [2] [3] [4]

Dockerfile permissions:

• Updated the chmod command in etc/opensearch/2.x/Dockerfile to use 755 instead of 777 for the .utm_geoip directory, enhancing container security.

Frontend installation instructions:

• Modified installation command strings in frontend/src/app/app-module/guides/guide-as400/constants.ts and frontend/src/app/app-module/guides/guide-linux-agent/guide-linux-agent.component.ts to set permissions to 755 instead of 777 for agent and collector installers, aligning user guidance with backend changes. [1] [2] [3] [4]