Prioritize external transcription endpoint over browser Web Speech API

Previously the on-device Web Speech API (Chrome/Edge/Safari) was always
preferred, and the configured external transcription endpoint was only
used as a fallback when the browser had no speech API at all (Firefox).

Flip the priority in Composer.tsx: if a transcription endpoint is
configured in Settings, use it for dictation regardless of browser
support, since it's generally far more accurate. Fall back to the
browser's on-device SpeechRecognition only when no endpoint is set.

Update the Settings hint text and README to describe the new behavior.
Rebuilt and redeployed to the repo root.

index.html

@@ -13,7 +13,7 @@
     <meta name="apple-mobile-web-app-status-bar-style" content="black-translucent" />
     <meta name="apple-mobile-web-app-title" content="Hermes" />
     <title>Hermes</title>
-    <script type="module" crossorigin src="/assets/index-Cbj_LrNG.js"></script>
+    <script type="module" crossorigin src="/assets/index-SBr79e_P.js"></script>
     <link rel="stylesheet" crossorigin href="/assets/index-CWSassUi.css">
   <link rel="manifest" href="/manifest.webmanifest"></head>
   <body>