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/transport/tor.rs

@@ -8,7 +8,6 @@ use anyhow::{Context, Result};
 use std::sync::atomic::{AtomicBool, Ordering};
 use std::time::Duration;
 
-const TOR_SOCKS: &str = "socks5h://127.0.0.1:9050";
 const TOR_TIMEOUT: Duration = Duration::from_secs(60);
 
 pub struct TorTransport {
@@ -49,7 +48,7 @@ impl TorTransport {
             "timestamp": chrono::Utc::now().to_rfc3339(),
         });
 
-        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(TOR_TIMEOUT)