feat: add nested locations support with parent-child hierarchy

[camdenwebster]

Implement comprehensive nested locations feature with the following capabilities:

Model Changes:

• Add parent relationship property to InventoryLocation
• Add helper methods: getChildren(), getDepth(), canAddChild(), getFullPath(), getAncestors(), isDescendant()
• Enforce 10-level depth limit for nested locations
• Support computed properties for hierarchy traversal

UI Updates:

• EditLocationView: Add parent location picker with depth indicator
• LocationItemCard: Show badge indicating child location count
• LocationsListView: Filter to show only root locations, search includes full path
• InventoryListSubView: Display child locations section when viewing a location
• InventoryListView: Add navigation support for child locations

Delete Workflow:

• Add confirmation dialog with options when deleting locations with children
• Option A: Cascade delete all child locations and unassign items
• Option B: Move children to different parent location via picker sheet
• MoveChildrenView: New sheet for selecting new parent when moving children

Search & Navigation:

• Search functionality includes nested location paths
• Sequential display of hierarchy with visual indicators
• Navigation from parent to child locations within InventoryListView