Add Plant Rooms/Zones feature for organizing plants by location

Implements Phase 3 of the feature roadmap:
- Room entity with 7 default rooms (Kitchen, Living Room, Bedroom, etc.)
- RoomRepositoryProtocol and CoreDataRoomRepository for persistence
- CreateDefaultRoomsUseCase and ManageRoomsUseCase for CRUD operations
- RoomsListView with swipe-to-delete and drag-to-reorder
- RoomEditorView with SF Symbol icon picker
- RoomPickerView for assigning plants to rooms
- Updated Plant entity (location → roomID) and PlantDetailView
- Added "Manage Rooms" section in SettingsView

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

PlantGuideTests/UpdatePlantUseCaseTests.swift

@@ -277,10 +277,11 @@ final class UpdatePlantUseCaseTests: XCTestCase {
         let originalPlant = createTestPlant(id: plantID, notes: "Original notes")
         mockRepository.addPlant(originalPlant)
 
+        let roomID = UUID()
         var updatedPlant = originalPlant
         updatedPlant.notes = "Updated notes"
         updatedPlant.customName = "My Monstera"
-        updatedPlant.location = "Living Room"
+        updatedPlant.roomID = roomID
 
         // When
         let result = try await sut.execute(plant: updatedPlant)
@@ -289,7 +290,7 @@ final class UpdatePlantUseCaseTests: XCTestCase {
         XCTAssertEqual(result.id, plantID)
         XCTAssertEqual(result.notes, "Updated notes")
         XCTAssertEqual(result.customName, "My Monstera")
-        XCTAssertEqual(result.location, "Living Room")
+        XCTAssertEqual(result.roomID, roomID)
 
         XCTAssertEqual(mockRepository.existsCallCount, 1)
         XCTAssertEqual(mockRepository.updatePlantCallCount, 1)
@@ -345,20 +346,21 @@ final class UpdatePlantUseCaseTests: XCTestCase {
         XCTAssertEqual(result.customName, "Bob the Plant")
     }
 
-    func testExecute_WhenUpdatingOnlyLocation_SuccessfullyUpdates() async throws {
+    func testExecute_WhenUpdatingOnlyRoomID_SuccessfullyUpdates() async throws {
         // Given
         let plantID = UUID()
         let originalPlant = createTestPlant(id: plantID)
         mockRepository.addPlant(originalPlant)
 
+        let kitchenRoomID = UUID()
         var updatedPlant = originalPlant
-        updatedPlant.location = "Kitchen windowsill"
+        updatedPlant.roomID = kitchenRoomID
 
         // When
         let result = try await sut.execute(plant: updatedPlant)
 
         // Then
-        XCTAssertEqual(result.location, "Kitchen windowsill")
+        XCTAssertEqual(result.roomID, kitchenRoomID)
     }
 
     func testExecute_PreservesImmutableProperties() async throws {