Improvement: Remove encoding fallback once SOVD server returns structured responses

[arvindr19]

Description

ServiceResolver::build_response() includes a fallback encoding path for when response metadata is unavailable from SOVD server. This should be removed once the SOVD server is updated to return properly structured (MDD-mapped) responses.

Current behavior:

• If MDD response metadata is unavailable, fallback constructs response by appending JSON values

Expected behavior:

• SOVD server returns responses in correct byte order with proper encoding
• Only metadata-driven encoding is used

Additional Context

Related file: service_resolver.rs (build_response() method)
Related PR: #11