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/crypto/hash.rs

@@ -64,6 +64,7 @@ pub fn crc32c(data: &[u8]) -> u32 {
 ///
 /// Returned buffer layout (IPv4):
 /// nonce_srv | nonce_clt | clt_ts | srv_ip | clt_port | purpose | clt_ip | srv_port | secret | nonce_srv | [clt_v6 | srv_v6] | nonce_clt
+#[allow(clippy::too_many_arguments)]
 pub fn build_middleproxy_prekey(
     nonce_srv: &[u8; 16],
     nonce_clt: &[u8; 16],
@@ -108,6 +109,7 @@ pub fn build_middleproxy_prekey(
 /// Uses MD5 + SHA-1 as mandated by the Telegram Middle Proxy protocol.
 /// These algorithms are NOT replaceable here — changing them would break
 /// interoperability with Telegram's middle proxy infrastructure.
+#[allow(clippy::too_many_arguments)]
 pub fn derive_middleproxy_keys(
     nonce_srv: &[u8; 16],
     nonce_clt: &[u8; 16],