fix: add clippy allow attributes for stable Rust compatibility

Add #[allow(...)] attributes to suppress clippy suggestions for
unstable features (let-chains, is_multiple_of) that would break
Docker builds using stable Rust.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: bordeux

src/functions/array.rs

@@ -327,6 +327,8 @@ pub fn array_group_by_fn(kwargs: Kwargs) -> Result<Value, Error> {
             })?;
 
             // Get the key value as string
+            // Note: Using nested if-let instead of let-chains for stable Rust compatibility
+            #[allow(clippy::collapsible_if)]
             if let Some(obj) = json_value.as_object() {
                 if let Some(key_val) = obj.get(&key) {
                     let group_key = match key_val {

src/functions/statistics.rs

@@ -201,6 +201,8 @@ pub fn array_median_fn(kwargs: Kwargs) -> Result<Value, Error> {
     numbers.sort_by(|a, b| a.partial_cmp(b).unwrap());
 
     let len = numbers.len();
+    // Note: Using modulo instead of is_multiple_of() for stable Rust compatibility
+    #[allow(clippy::manual_is_multiple_of)]
     let median = if len % 2 == 0 {
         // Even length: average of two middle values
         (numbers[len / 2 - 1] + numbers[len / 2]) / 2.0