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/container/data_manager.rs

@@ -64,29 +64,6 @@ impl DevDataManager {
         // This is a no-op by default, but can be extended
         Ok(())
     }
-
-    /// Get all app data directories
-    #[allow(dead_code)]
-    pub async fn list_app_data_dirs(&self) -> Result<Vec<String>> {
-        if !self.dev_data_dir.exists() {
-            return Ok(vec![]);
-        }
-
-        let mut entries = fs::read_dir(&self.dev_data_dir)
-            .await
-            .with_context(|| format!("Failed to read dev data directory: {:?}", self.dev_data_dir))?;
-
-        let mut app_ids = Vec::new();
-        while let Some(entry) = entries.next_entry().await? {
-            if entry.file_type().await?.is_dir() {
-                if let Some(name) = entry.file_name().to_str() {
-                    app_ids.push(name.to_string());
-                }
-            }
-        }
-
-        Ok(app_ids)
-    }
 }
 
 #[cfg(test)]