Modernize remaining interface{} to any in context.go

[vishr]

Summary

Completes the modernization of context.go by replacing all remaining interface{} types with any.

Changes:

• Updated Context interface method signatures (23 occurrences)
• Updated implementation method signatures
• Methods affected: Get, Set, Bind, Validate, Render, JSON*, XML*, JSONP

Benefits:

• Improved code readability
• Follows Go 1.18+ best practices
• Consistent with modern Go codebases

Test plan

• [x] All existing tests pass
• [x] Linting passes
• [x] No behavioral changes

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