refactor: centralize constants, eliminate unwraps, remove dead code, resolve TODOs

- R13+R16: Replace .expect() with .context()? in main.rs and identity.rs
- R17+R18+R19: Fix unwrap() calls in helpers and js-engine
- R20+R21: Remove #[allow(dead_code)] annotations and delete truly dead code
- R22-R26: Create constants.rs module, replace 21 hardcoded values across 12 files
- R28+R29: LND/DWN timeouts already present — verified
- R30-R33: Remove TODO comments, implement marketplace payment check

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

core/archipelago/src/node_message.rs

@@ -7,7 +7,6 @@ use serde::{Deserialize, Serialize};
 use std::path::{Path, PathBuf};
 use std::sync::{Mutex, OnceLock};
 
-const TOR_SOCKS: &str = "socks5h://127.0.0.1:9050";
 const MAX_STORED: usize = 200;
 
 #[derive(Debug, Clone, Serialize, Deserialize)]
@@ -263,7 +262,7 @@ pub async fn send_to_peer(
         "encrypted": encrypted,
     });
 
-    let proxy = reqwest::Proxy::all(TOR_SOCKS).context("Invalid Tor proxy")?;
+    let proxy = reqwest::Proxy::all(crate::constants::TOR_SOCKS_PROXY).context("Invalid Tor proxy")?;
     let client = reqwest::Client::builder()
         .proxy(proxy)
         .timeout(std::time::Duration::from_secs(60))
@@ -306,7 +305,7 @@ pub async fn check_peer_reachable(onion: &str) -> Result<bool> {
         format!("{}.onion", onion)
     };
     let url = format!("http://{}/health", host);
-    let proxy = reqwest::Proxy::all(TOR_SOCKS).context("Invalid Tor proxy")?;
+    let proxy = reqwest::Proxy::all(crate::constants::TOR_SOCKS_PROXY).context("Invalid Tor proxy")?;
     let client = reqwest::Client::builder()
         .proxy(proxy)
         .timeout(std::time::Duration::from_secs(30))