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- Remove outdated dependencies and update dependency versions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

paginate.rs

@@ -19,7 +19,7 @@ pub fn paginate<T: Clone>(items: &[T], pagination: Option<&Pagination>) -> (Vec<
         .unwrap_or(0)
         .min(items.len());
 
-    let end = std::cmp::min(start_offset + page_size, items.len());
+    let end = start_offset.saturating_add(page_size).min(items.len());
     let has_next = end < items.len();
     let next_page_token = if has_next {
         end.to_string()