refactor: replace blocking std::fs and TCP I/O with async tokio equivalents

- R6: Convert 6 std::fs calls in session.rs to tokio::fs async
- R7: Convert std::fs::read_to_string in docker_packages.rs to async
- R8: Convert 3 std::fs calls in port_allocator.rs to async, switch to tokio::sync::Mutex
- R9+R10+R11: Fix blocking I/O in node_message.rs and nostr_discovery.rs
- R12: Convert electrs_status.rs from sync TCP to async tokio::net with 5s timeouts
- R4+R5: Spawn periodic cleanup tasks for endpoint and login rate limiters

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

core/archipelago/src/container/docker_packages.rs

@@ -141,7 +141,7 @@ impl DockerPackageScanner {
             // Convert container state to package/service state
             let (package_state, service_status) = convert_state(&container.state);
             
-            let tor_address = read_tor_address(&app_id);
+            let tor_address = read_tor_address(&app_id).await;
 
             let package = PackageDataEntry {
                 state: package_state.clone(),
@@ -548,7 +548,7 @@ fn is_real_onion_address(s: &str) -> bool {
 /// Read real .onion address from Tor hidden service hostname file.
 /// Service name "archipelago" is for the main web UI (nginx port 80).
 /// Uses TOR_DATA_DIR env var if set, else /var/lib/archipelago/tor.
-pub fn read_tor_address(app_id: &str) -> Option<String> {
+pub async fn read_tor_address(app_id: &str) -> Option<String> {
     let service = tor_service_name(app_id)?;
     let base = std::env::var("TOR_DATA_DIR").unwrap_or_else(|_| "/var/lib/archipelago/tor".to_string());
 
@@ -558,7 +558,8 @@ pub fn read_tor_address(app_id: &str) -> Option<String> {
         .unwrap_or(std::path::Path::new("/var/lib/archipelago"))
         .join("tor-hostnames")
         .join(service);
-    if let Some(addr) = std::fs::read_to_string(&hostnames_path)
+    if let Some(addr) = tokio::fs::read_to_string(&hostnames_path)
+        .await
         .ok()
         .map(|s| s.trim().to_string())
         .filter(|s| s.ends_with(".onion") && !s.is_empty())
@@ -570,7 +571,8 @@ pub fn read_tor_address(app_id: &str) -> Option<String> {
     let path = std::path::Path::new(&base)
         .join(format!("hidden_service_{}", service))
         .join("hostname");
-    std::fs::read_to_string(&path)
+    tokio::fs::read_to_string(&path)
+        .await
         .ok()
         .map(|s| s.trim().to_string())
         .filter(|s| s.ends_with(".onion") && !s.is_empty())