fix: resolve clippy warnings

Reduce clippy warnings from54 to16 by fixing mechanical issues:

- collapsible_if: collapse nested if-let chains with let-chains
- clone_on_copy: remove unnecessary .clone() on Copy types
- manual_clamp: replace .max().min() with .clamp()
- unnecessary_cast: remove redundant type casts
- collapsible_else_if: flatten else-if chains
- contains_vs_iter_any: replace .iter().any() with .contains()
- unnecessary_closure: replace .or_else(|| x) with .or(x)
- useless_conversion: remove redundant .into() calls
- is_none_or: replace .map_or(true, ...) with .is_none_or(...)
- while_let_loop: convert loop with if-let-break to while-let

Remaining16 warnings are design-level issues (too_many_arguments,
await_holding_lock, type_complexity, new_ret_no_self) that require
architectural changes to fix.

src/network/stun.rs

@@ -198,16 +198,11 @@ async fn resolve_stun_addr(stun_addr: &str, family: IpFamily) -> Result<Option<S
         });
     }
 
-    let addrs = lookup_host(stun_addr)
+    let mut addrs = lookup_host(stun_addr)
         .await
         .map_err(|e| ProxyError::Proxy(format!("STUN resolve failed: {e}")))?;
 
     let target = addrs
-        .filter(|a| match (a.is_ipv4(), family) {
-            (true, IpFamily::V4) => true,
-            (false, IpFamily::V6) => true,
-            _ => false,
-        })
-        .next();
+        .find(|a| matches!((a.is_ipv4(), family), (true, IpFamily::V4) | (false, IpFamily::V6)));
     Ok(target)
 }