refactor: replace Box<dyn Error> with anyhow::Result

- ingestion_pipeline::run_worker_loop returns anyhow::Result<()>
- api_router::ApiState::new returns anyhow::Result<Self>
- html_router::HtmlState::new_with_resources is infallible, returns Self
- main/server/worker binary entry points return anyhow::Result<()>

main/src/worker.rs

@@ -11,7 +11,7 @@ use tracing::info;
 use tracing_subscriber::{fmt, prelude::*, EnvFilter};
 
 #[tokio::main]
-async fn main() -> Result<(), Box<dyn std::error::Error>> {
+async fn main() -> anyhow::Result<()> {
     // Set up tracing
     tracing_subscriber::registry()
         .with(fmt::layer())