refactor(cache): redesign cache system with structured keys and improved performance

- Add repo_path parameter to cached_response and cached_vec_response functions
- Implement structured cache key format with namespace, repo_path, and request proto
- Replace global cache with Moka in-memory cache using weight-based eviction
- Set 256MB memory cap with 10-minute TTL and 2-minute TTI policy
- Add metrics collection for cache operations and evictions
- Implement efficient repo-scoped invalidation using key structure
- Add detailed documentation comments explaining cache architecture
- Remove outdated dependencies and update dependency versions
- Add error handling for encoding failures in cache operations
- Optimize Vec responses with length-delimited encoding and pre-allocation

diff/get_diff_stats.rs

@@ -17,6 +17,12 @@ pub(crate) fn diff_stats_for_range(
     head: &str,
     options: Option<&crate::pb::DiffOptions>,
 ) -> GitResult<crate::pb::DiffStats> {
+    if let Some(options) = options {
+        for path in &options.pathspec {
+            crate::sanitize::validate_file_path(path)?;
+        }
+    }
+
     let mut args = vec![
         "--git-dir".to_string(),
         repo.bare_dir.to_string_lossy().into_owned(),