feat: comprehensive model management enhancements and platform fixes

- Block 1: Refactored path logic into a centralized PathResolver for OS-agnostic and relative path handling.
- Block 2: Improved platform compatibility (shutdown, macOS menu, System Tray fallback).
- Block 3: Added Power-User features (Model Updater, Smart Cleanup, Thumbnails, Node Sync, Remote Status).
- Fixes: Recursive subfolder scanning, archive detection logic, and UI progress throttling.

src/main/java/de/tki/comfymodels/service/ICleanupService.java

@@ -0,0 +1,19 @@
+package de.tki.comfymodels.service;
+
+import de.tki.comfymodels.domain.ModelInfo;
+import java.util.List;
+
+/**
+ * Service for scanning and cleaning up unused models.
+ */
+public interface ICleanupService {
+    /**
+     * Identifies models that haven't been accessed for the given number of months.
+     */
+    List<ModelInfo> findUnusedModels(int monthsThreshold);
+
+    /**
+     * Archives the specified models.
+     */
+    void archiveModels(List<ModelInfo> models, java.util.function.BiConsumer<Integer, String> onStatusUpdate, Runnable onFinished);
+}