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- Remove outdated dependencies and update dependency versions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

branch/get_branch.rs

@@ -4,6 +4,7 @@ use crate::pb::{Branch, GetBranchRequest};
 
 impl GitBare {
     pub fn get_branch(&self, request: GetBranchRequest) -> GitResult<Branch> {
+        crate::sanitize::validate_ref_name(&request.name)?;
         let repo = self.gix_repo()?;
         let refname = format!("refs/heads/{}", request.name);
         let mut r = repo.find_reference(refname.as_str())?;