feat: consume new semantic token and automatic light and dark mode theming

[SagarRajput-7]

Pull Request

Reference - SigNoz/design-tokens#30

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📄 Summary

Why does this change exist?
What problem does it solve, and why is this the right approach?

Screenshots / Screen Recordings (if applicable)

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Issues closed by this PR

Reference issues using Closes #issue-number to enable automatic closure on merge.

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✅ Change Type

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• ✨ Feature
• 🐛 Bug fix
• ♻️ Refactor
• 🛠️ Infra / Tooling
• 🧪 Test-only

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🐛 Bug Context

Required if this PR fixes a bug

Root Cause

What caused the issue?
Regression, faulty assumption, edge case, refactor, etc.

Fix Strategy

How does this PR address the root cause?

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🧪 Testing Strategy

How was this change validated?

• Tests added/updated:
• Manual verification:
• Edge cases covered:

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⚠️ Risk & Impact Assessment

What could break? How do we recover?

• Blast radius:
• Potential regressions:
• Rollback plan:

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📝 Changelog

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Use N/A for internal or non-user-facing changes

Field	Value
Deployment Type	Cloud / OSS / Enterprise
Change Type	Feature / Bug Fix / Maintenance
Description	User-facing summary

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📋 Checklist

• Tests added or explicitly not required
• Manually tested
• Breaking changes documented
• Backward compatibility considered

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👀 Notes for Reviewers

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