What this PR does / why we need it?

Refs #11843

Summary of your change

Backend (Core):

• Added fontFamily field to TerminalInfo DTO (core/app/dto/setting.go)
• Updated terminal settings service to handle font family persistence (core/app/service/setting.go)
• Created database migration to add FontFamily setting (core/init/migration/migrations/init.go)

Frontend:

• Added custom font input field in terminal settings page (src/views/terminal/setting/index.vue)
• Implemented real-time font preview and live updates for open terminals (src/components/terminal/index.vue)
• Added font family state management in Pinia store (src/store/modules/terminal.ts)

Please indicate you've done the following:

• Made sure tests are passing and test coverage is added if needed.
• Made sure commit message follow the rule of Conventional Commits specification.
• Considered the docs impact and opened a new docs issue or PR with docs changes if needed.

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