feat: Add transcription worker and state management

Introduce an `AppState` struct to hold shared application state,
including configuration and the transcription sender.
Modify `create_router` and `create_router_with_state` to use `AppState`.
Update `main.rs` to initialize the transcription worker and pass the
`AppState` to the router.
Implement the transcription worker logic in
`server/src/transcribe/worker.rs`, handling job queues, FFmpeg remuxing,
and Whisper transcription.
Update `server/src/auth.rs` to use `Arc<Config>` from the shared state.
Modify `server/src/routes/upload.rs` to enqueue transcription jobs and
handle potential errors.
Add `TranscribeJob` and channel types in `server/src/transcribe/mod.rs`.

server/src/auth.rs

@@ -1,7 +1,7 @@
 use std::path::PathBuf;
 use std::sync::Arc;
 
-use axum::extract::FromRequestParts;
+use axum::extract::{FromRef, FromRequestParts};
 use axum::http::request::Parts;
 
 use crate::config::Config;
@@ -14,31 +14,34 @@ pub struct AuthenticatedUser {
     pub data_dir: PathBuf,
 }
 
-impl FromRequestParts<Arc<Config>> for AuthenticatedUser {
+impl<S> FromRequestParts<S> for AuthenticatedUser
+where
+    S: Send + Sync,
+    Arc<Config>: FromRef<S>,
+{
     type Rejection = AppError;
 
-    async fn from_request_parts(
-        parts: &mut Parts,
-        state: &Arc<Config>,
-    ) -> Result<Self, Self::Rejection> {
+    async fn from_request_parts(parts: &mut Parts, state: &S) -> Result<Self, Self::Rejection> {
+        let config = Arc::<Config>::from_ref(state);
+
         let api_key = parts
             .headers
             .get("X-API-Key")
             .and_then(|v| v.to_str().ok())
             .ok_or(AppError::Unauthorized)?;
 
-        let slug = state
+        let slug = config
             .api_keys
             .get(api_key)
             .ok_or(AppError::Unauthorized)?;
 
-        let user = state
+        let user = config
             .users
             .iter()
             .find(|u| u.slug == *slug)
             .ok_or(AppError::Unauthorized)?;
 
-        let data_dir = state.data_path.join(slug);
+        let data_dir = config.data_path.join(slug);
         tokio::fs::create_dir_all(data_dir.join("open")).await?;
         tokio::fs::create_dir_all(data_dir.join("done")).await?;