feat: copy transcript to Obsidian vault on open

Config: obsidian.vault path. On Obsidian button click, file is copied to
vault dir then opened via obsidian:// URI. Vault path configurable in settings.

frontend/settings.js

@@ -62,6 +62,7 @@ async function loadConfig() {
   const diarCfg = cfg.diarization || {};
   document.getElementById('diar-enabled').checked = !!diarCfg.enabled;
   document.getElementById('diar-hf-token').value = diarCfg.hf_token || '';
+  document.getElementById('obsidian-vault').value = (cfg.obsidian && cfg.obsidian.vault) || '';
 }
 
 document.getElementById('refresh-devices-btn').addEventListener('click', loadDevices);
@@ -103,6 +104,9 @@ document.getElementById('save-btn').addEventListener('click', async function() {
       base_url: document.getElementById('ollama-url').value,
       model: document.getElementById('ollama-model').value,
     },
+    obsidian: {
+      vault: document.getElementById('obsidian-vault').value.trim(),
+    },
     diarization: {
       enabled: document.getElementById('diar-enabled').checked,
       hf_token: document.getElementById('diar-hf-token').value.trim(),