perf: remove dead redirect middleware (ran on every request doing nothing)

The redirect middleware was a leftover from the custom HTTP server → Axum
migration. It executed on every single request (including static files),
allocating a String from the URI path and performing 3 starts_with() checks,
but never actually redirected anything — just debug logging.

- Remove middleware application from main.rs
- Remove pub mod redirect from middleware/mod.rs
- Delete redirect.rs (121 lines of dead code)

Saves ~80-170ns of overhead per request (String alloc + comparisons +
Tower layer dispatch).

src/main.rs

@@ -269,10 +269,6 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
         }
     }
 
-    // Apply the redirect middleware for legacy routes
-    use oxicloud::interfaces::middleware::redirect::redirect_middleware;
-    app = app.layer(axum::middleware::from_fn(redirect_middleware));
-
     // Increase the default body limit to 10 GB to allow large file uploads.
     // Without this Axum caps Multipart bodies at 2 MB.
     app = app.layer(DefaultBodyLimit::max(10 * 1024 * 1024 * 1024));