feat(repository): add language statistics analysis feature

- Remove data directory from gitignore to include language data
- Add build script to parse linguist languages.yml and generate static mappings
- Include serde and serde_yml dependencies for YAML parsing
- Add lang_stats module with language detection and statistics calculation
- Generate protobuf definitions for language statistics API endpoints
- Implement GetLanguageStats RPC endpoint in repository server
- Add comprehensive test suite for language statistics functionality
- Include extension and filename based language detection logic
- Implement binary file classification and group resolution features

server/repository.rs

@@ -850,4 +850,21 @@ impl repository_service_server::RepositoryService for GitksService {
         m.record("ok");
         Ok(tonic::Response::new(resp))
     }
+
+    async fn get_language_stats(
+        &self,
+        request: tonic::Request<GetLanguageStatsRequest>,
+    ) -> Result<tonic::Response<GetLanguageStatsResponse>, tonic::Status> {
+        let m = crate::metrics::RequestMetrics::new("gitks.RepositoryService/GetLanguageStats");
+        let inner = request.into_inner();
+        let _rate = self.acquire_rate_limit(inner.repository.as_ref()).await?;
+        let repo = self.repo_label(inner.repository.as_ref());
+        let span = tracing::info_span!("repo.get_language_stats", %repo);
+        let _enter = span.enter();
+        let gb = self.resolve(inner.repository.as_ref())?;
+        let resp = gb.get_language_stats(inner).map_err(into_status)?;
+        tracing::info!(%repo, languages = resp.languages.len(), "language stats done");
+        m.record("ok");
+        Ok(tonic::Response::new(resp))
+    }
 }