Use std::string_view for mode names

[JanPetterMG]

Refactors mode name handling to use std::string_view instead of owning string types.

This reduces unnecessary allocations and improves overall efficiency, especially in static and compile-time contexts where service names are immutable.

Changes

• Replace mode name storage with std::string_view
• Update constructors and interfaces to accept non-owning string references
• Remove redundant string allocations and copies

Impact

• No functional changes
• Improved performance and memory usage
• Safer and clearer API contracts