perf: optimize FeatureService.UpdateFeature

[nnnkkk7]

Describe the feature you'd like

Problem

This method is a bit slow due to unnecessary processing of all features.

Root Causes

1. Full Feature Retrieval: Fetches ALL features instead of target feature only
2. Complete Dependency Validation: Validates all features, not just the modified one
3. Heavy JSON Updates: MySQL JSON column operations are expensive
4. Synchronous External Calls: Blocking cache refresh and event publishing

Background

No response

Alternative solutions

No response