[Frontend] Remove unsafe casts and type the theme union

[grantfox-oss]

Telegram (ask questions / claim the issue here first): https://t.me/+DOylgFv1jyJlNzM0

Why this matters

src/app/[locale]/settings/page.tsx calls setTheme(opt as any) and src/instrumentation.ts uses any for log args. These casts defeat the type checker on a settings control that changes global state. Typing them properly prevents invalid theme values.

Acceptance criteria

• Define a Theme union type (for example light, dark, system) and use it in the store and setter
• Remove the as any in settings so invalid options fail type checking
• Replace any[] in src/instrumentation.ts with a precise type
• Grep for other as any in src and fix or justify each with a comment

Files to touch

• src/app/[locale]/settings/page.tsx
• src/app/stores/useThemeStore.ts
• src/instrumentation.ts

Out of scope

• Adding new themes

[temisan0x]

hey team, i’d like to take on this issue
I’ve been able to go through it
I can start on it now if it’s okay

[SudiptaPaul-31]

May I be assigned to this issue please my name is Sudipta Paul a active open source contributor with more than 50+ merged pr's and also an active contributor of GrantFox from begining and would love to work on this issue and get a pr merged

[grantfox-oss]

🦊 GrantFox — @SudiptaPaul-31 has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #14)
2. Your PR will be reviewed by the LabsCrypt maintainers

Good luck! Track your progress on GrantFox.

[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Official Campaign campaign!

@SudiptaPaul-31's PR #26 was approved and merged by @ogazboiz.

🏆 @SudiptaPaul-31: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (328 total points). Track your full progress on GrantFox.

👏 Great work, @SudiptaPaul-31! Keep contributing to LabsCrypt.