Fix Ollama settings on startup + video extraction UX

AI provider:
- Extract configureAIProvider() from saveSettings for reuse
- Call it on app startup after sidecar is ready (was only called on Save)
- Call it after first-time sidecar download completes
- Sidecar now receives correct Ollama URL/model immediately

Video extraction:
- Hide ffmpeg console window on Windows (CREATE_NO_WINDOW flag)
- Show "Extracting audio from video..." overlay with spinner during extraction
- UI stays responsive while ffmpeg runs

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

src-tauri/src/commands/media.rs

@@ -1,6 +1,9 @@
 use std::path::PathBuf;
 use std::process::Command;
 
+#[cfg(target_os = "windows")]
+use std::os::windows::process::CommandExt;
+
 /// Extract audio from a video file to a WAV file using ffmpeg.
 /// Returns the path to the extracted audio file.
 #[tauri::command]
@@ -23,8 +26,8 @@ pub fn extract_audio(file_path: String) -> Result<String, String> {
     // Find ffmpeg — check sidecar extract dir first, then system PATH
     let ffmpeg = find_ffmpeg().ok_or("ffmpeg not found. Install ffmpeg or ensure it's in PATH.")?;
 
-    let status = Command::new(&ffmpeg)
-        .args([
+    let mut cmd = Command::new(&ffmpeg);
+    cmd.args([
             "-y",             // Overwrite output
             "-i",
             &file_path,
@@ -38,7 +41,13 @@ pub fn extract_audio(file_path: String) -> Result<String, String> {
         ])
         .arg(output.to_str().unwrap())
         .stdout(std::process::Stdio::null())
-        .stderr(std::process::Stdio::piped())
+        .stderr(std::process::Stdio::piped());
+
+    // Hide the console window on Windows (CREATE_NO_WINDOW = 0x08000000)
+    #[cfg(target_os = "windows")]
+    cmd.creation_flags(0x08000000);
+
+    let status = cmd
         .status()
         .map_err(|e| format!("Failed to run ffmpeg: {e}"))?;