chore: fix & enhance msg content

[ZuzooVn]

Checklist:

[!IMPORTANT]
Please review the checklist below before submitting your pull request.

• [x] Please open an issue before creating a PR or link to an existing issue
• [x] I have performed a self-review of my own code
• [x] I have commented my code, particularly in hard-to-understand areas
• [x] I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods

Description

• Improved error messages to provide more context and guidance to users
• Removed trailing periods from all error messages for a cleaner look

Type of Change

• [x] Improvement, including but not limited to code refactoring, performance optimization, and UI/UX improvement

[ZuzooVn]

Sorry but I think we should keep the ..

@crazywoola

Could you please reopen this pull request?

I will add a period (".") at the end of all messages. Currently, there's inconsistency in this regard - some messages have a period, while others don't.