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- Remove outdated dependencies and update dependency versions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

Dockerfile

@@ -22,9 +22,11 @@ RUN apt-get update && \
     apt-get install -y --no-install-recommends git ca-certificates && \
     rm -rf /var/lib/apt/lists/*
 COPY --from=builder /app/target/release/gitks /usr/local/bin/gitks
+
 ENV GITKS_HOST=0.0.0.0
 ENV GITKS_PORT=50051
 ENV REPO_PREFIX_PATH=/data/repos
+
 RUN mkdir -p /data/repos
 EXPOSE 50051
-ENTRYPOINT ["gitks"]
+ENTRYPOINT ["gitks"]