chore: senior-review cleanup pass

- Remove Gemini's committed update_*.py regex-surgery scripts
- Drop unused iroh-tickets dependency (hand-rolled ticket is used instead)
- Replace ToString antipattern with Display impl on PeerSpeakTicket
- Route debug log to XDG state/cache dir instead of hardcoded /home path
- Clear all compiler + clippy warnings (unused imports, collapsible ifs,
  redundant pattern matching, missing Default)

Builds clean with zero warnings.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/config.rs

@@ -29,13 +29,11 @@ impl AppConfig {
     }
 
     pub fn load() -> Self {
-        if let Some(path) = Self::config_path() {
-            if let Ok(contents) = fs::read_to_string(&path) {
-                if let Ok(config) = serde_json::from_str(&contents) {
+        if let Some(path) = Self::config_path()
+            && let Ok(contents) = fs::read_to_string(&path)
+                && let Ok(config) = serde_json::from_str(&contents) {
                     return config;
                 }
-            }
-        }
         Self::default()
     }