Add transcribator page: audio recording + Whisper STT proxy

Browser records audio via MediaRecorder API, bcard proxies it to
Whisper STT service and returns transcription as JSON.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Cargo.toml

@@ -4,5 +4,8 @@ version = "0.1.0"
 edition = "2021"
 
 [dependencies]
-axum = "0.7"
+axum = { version = "0.7", features = ["multipart"] }
+reqwest = { version = "0.12", features = ["multipart", "json"] }
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
 tokio = { version = "1", features = ["full"] }