Modernize codebase: replace interface{} with any

[paganotoni]

This PR modernizes the codebase by replacing deprecated patterns with modern Go idioms:

Changes

1. Replace interface{} with any (Go 1.18+)

• Replaced 104 occurrences of interface{} with any across 41 files
• Updated error message strings to reference map[string]any instead of map[string]interface{}
• This change leverages the type alias added in Go 1.18 for cleaner, more readable code

2. Update error handling (Go 1.13+ best practice)

• Replaced os.IsNotExist(err) with errors.Is(err, os.ErrNotExist) in route_mappings.go
• This is the recommended approach for error handling since Go 1.13

Testing

All tests pass successfully:

• go test -shuffle on ./... passes for all packages
• No functional changes, purely syntactic modernization