chore(security,refactor): extract sanitization and improve code quality (#41)

* chore(security,refactor): extract sanitization and improve code quality

- [x] Extract sanitization functions to dedicated sanitization.go module
- [x] Add comprehensive golangci-lint v2 configuration with security rules
- [x] Replace interface{} with any type throughout codebase
- [x] Add admin API authentication security warning
- [x] Extract WebSocket and stats streaming constants
- [x] Add best-effort error handling comments for resource cleanup
- [x] Expand sensitive field patterns for improved PII redaction
- [x] Simplify safety checks and remove redundant nil validations
- [x] Improve test coverage for password field redaction patterns

* refactor: replace interface{} with any type alias

- [x] Replace all `map[string]interface{}` with `map[string]any`
- [x] Replace all `interface{}` with `any` in function signatures and type definitions
- [x] Update sync.Pool New function returns from `interface{}` to `any`
- [x] Add package documentation comments to 8 package files
- [x] Update type assertions and casts to work with `any` type

graphql_test.go

@@ -486,7 +486,7 @@ func (suite *Tests) Test_DeepIntrospectionQueries() {
 			for _, q := range tt.allowed {
 				introspectionAllowedQueries[strings.ToLower(q)] = struct{}{}
 			}
-			body := map[string]interface{}{
+			body := map[string]any{
 				"query": tt.query,
 			}
 			bodyBytes, _ := json.Marshal(body)