docs: mark Hetzner Provider and Register Instances features as completed

- Move Hetzner Provider Support from Active to Completed (Dec 1, 2025)
- Move Register Existing Instances from Active to Completed (Nov 19, 2025)
- Both features have been fully implemented and merged

Author: josecelano

docs/features/README.md

@@ -13,21 +13,21 @@ Feature documentation serves to:
 
 ## 📁 Active Features
 
-| Feature                                                              | Status         | Priority | Created      |
-| -------------------------------------------------------------------- | -------------- | -------- | ------------ |
-| [JSON Schema Generation](./json-schema-generation/README.md)         | 📋 Specified   | High     | Dec 12, 2025 |
-| [Hetzner Provider Support](./hetzner-provider-support/README.md)     | 📋 Specified   | High     | Dec 1, 2025  |
-| [Register Existing Instances](./import-existing-instances/README.md) | 📋 Specified   | High     | Nov 19, 2025 |
-| [Linter Auto-fix](./linter-auto-fix/README.md)                       | 📋 Specified   | Medium   | Oct 9, 2025  |
-| [Linter Parallel Execution](./linter-parallel-execution/README.md)   | ⏸️ Deferred    | Low      | Oct 9, 2025  |
-| [Environment State Management](./environment-state-management/)      | 🔄 Refactoring | High     | Sept 9, 2025 |
+| Feature                                                            | Status         | Priority | Created      |
+| ------------------------------------------------------------------ | -------------- | -------- | ------------ |
+| [JSON Schema Generation](./json-schema-generation/README.md)       | 📋 Specified   | High     | Dec 12, 2025 |
+| [Linter Auto-fix](./linter-auto-fix/README.md)                     | 📋 Specified   | Medium   | Oct 9, 2025  |
+| [Linter Parallel Execution](./linter-parallel-execution/README.md) | ⏸️ Deferred    | Low      | Oct 9, 2025  |
+| [Environment State Management](./environment-state-management/)    | 🔄 Refactoring | High     | Sept 9, 2025 |
 
 ## ✅ Completed Features
 
-| Feature                                                            | Completed   | Description                                                         |
-| ------------------------------------------------------------------ | ----------- | ------------------------------------------------------------------- |
-| Persistent Logging with Optional Stderr                            | Oct 9, 2025 | LoggingBuilder with fluent API for file and optional stderr logging |
-| [Environment-Aware Logging](./environment-aware-logging/README.md) | Oct 9, 2025 | Multi-environment log visibility with proper span hierarchy         |
+| Feature                                                              | Completed    | Description                                                           |
+| -------------------------------------------------------------------- | ------------ | --------------------------------------------------------------------- |
+| [Hetzner Provider Support](./hetzner-provider-support/README.md)     | Dec 1, 2025  | Multi-provider architecture with Hetzner Cloud as production provider |
+| [Register Existing Instances](./import-existing-instances/README.md) | Nov 19, 2025 | Register command to import already-provisioned instances              |
+| Persistent Logging with Optional Stderr                              | Oct 9, 2025  | LoggingBuilder with fluent API for file and optional stderr logging   |
+| [Environment-Aware Logging](./environment-aware-logging/README.md)   | Oct 9, 2025  | Multi-environment log visibility with proper span hierarchy           |
 
 **Note**: Completed features remain in the repository for reference. Full implementation history is available in git history.