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/transport/middle_proxy/health.rs

@@ -92,10 +92,10 @@ async fn check_family(
 
         let key = (dc, family);
         let now = Instant::now();
-        if let Some(ts) = next_attempt.get(&key) {
-            if now < *ts {
-                continue;
-            }
+        if let Some(ts) = next_attempt.get(&key)
+            && now < *ts
+        {
+            continue;
         }
 
         let max_concurrent = pool.me_reconnect_max_concurrent_per_dc.max(1) as usize;