Parse and Display Deduplication Status (HTTP only)

[swarna1101]

CLI currently prints raw JSON response body. Parse the status field from HTTP publish response and show different messages: "✅ Published" vs "⚠️ Deduplicated (already sent to subscribers)".

Why: Users see "Published" even when proxy drops duplicates. The info is already in the response, CLI just doesn't parse it.

NOTE: gRPC proxy doesn't implement deduplication yet (always returns "published"), so this only works for HTTP mode.