feat: Gitea repo indexing via gRPC ReindexCode endpoint

Gitea indexer (code_index/gitea.rs):
- Walks repos via GiteaClient API (list repos → traverse dirs → fetch files)
- Base64 decodes file content from Gitea API responses
- Extracts symbols with tree-sitter (Rust, TypeScript, Python)
- Indexes to sol_code OpenSearch index with repo/branch/source metadata
- Skips hidden dirs, vendor, node_modules, files >100KB
- delete_branch() for clean re-indexing

Server-side tree-sitter (code_index/symbols.rs):
- Full symbol extraction shared with CLI client
- extract_symbols(), extract_project_symbols(), detect_language()

gRPC ReindexCode RPC:
- ReindexCodeRequest: org, repo, branch (all optional filters)
- ReindexCodeResponse: repos_indexed, symbols_indexed, error
- Uses ToolRegistry's GiteaClient (already authenticated)
- Creates sol_code index if not exists

ToolRegistry.gitea_client() accessor for reindex endpoint.

Cargo.toml

@@ -44,6 +44,10 @@ prost = "0.14"
 tokio-stream = "0.1"
 jsonwebtoken = "9"
 tokenizers = { version = "0.22", default-features = false, features = ["onig", "http"] }
+tree-sitter = "0.24"
+tree-sitter-rust = "0.23"
+tree-sitter-typescript = "0.23"
+tree-sitter-python = "0.23"
 
 [dev-dependencies]
 dotenv = "0.15"