feat(ui): replace loading indicators with Apple-style LoadingSpinner

- Add LoadingSpinner component with small/medium/large sizes using system gray color
- Add LoadingPlaceholder for skeleton loading states
- Add LoadingSheet for full-screen blocking overlays
- Replace ThemedSpinner/ThemedSpinnerCompact across all views
- Remove deprecated loading components from AnimatedComponents.swift
- Delete LoadingTextGenerator.swift
- Fix PhotoImportView layout to fill full width

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

SportsTimeTests/Loading/LoadingSpinnerTests.swift

@@ -0,0 +1,47 @@
+//
+//  LoadingSpinnerTests.swift
+//  SportsTimeTests
+//
+
+import Testing
+import SwiftUI
+@testable import SportsTime
+
+struct LoadingSpinnerTests {
+
+    @Test func smallSizeHasCorrectDimensions() {
+        let config = LoadingSpinner.Size.small
+        #expect(config.diameter == 16)
+        #expect(config.strokeWidth == 2)
+    }
+
+    @Test func mediumSizeHasCorrectDimensions() {
+        let config = LoadingSpinner.Size.medium
+        #expect(config.diameter == 24)
+        #expect(config.strokeWidth == 3)
+    }
+
+    @Test func largeSizeHasCorrectDimensions() {
+        let config = LoadingSpinner.Size.large
+        #expect(config.diameter == 40)
+        #expect(config.strokeWidth == 4)
+    }
+
+    @Test func spinnerCanBeCreatedWithAllSizes() {
+        let small = LoadingSpinner(size: .small)
+        let medium = LoadingSpinner(size: .medium)
+        let large = LoadingSpinner(size: .large)
+
+        #expect(small.size == .small)
+        #expect(medium.size == .medium)
+        #expect(large.size == .large)
+    }
+
+    @Test func spinnerCanHaveOptionalLabel() {
+        let withLabel = LoadingSpinner(size: .medium, label: "Loading...")
+        let withoutLabel = LoadingSpinner(size: .medium)
+
+        #expect(withLabel.label == "Loading...")
+        #expect(withoutLabel.label == nil)
+    }
+}