feat: add justified layout modes and aspect-ratio-aware mosaic (#146)

- Add Flickr justified-layout and react-photo-album as masonry mode options
- Implement aspect-ratio-aware mosaic layout that dynamically selects
  patterns based on photo orientations to minimize cropping
- Add 9 mosaic pattern types optimized for different orientation combinations
- Add theme customizer options for masonry mode selection (columns/rows/flickr/justified)
- Add i18n translations for new layout options

frontend/src/types/justified-layout.d.ts

@@ -0,0 +1,38 @@
+declare module 'justified-layout' {
+  interface JustifiedLayoutOptions {
+    containerWidth: number;
+    containerPadding?: number | { top: number; right: number; bottom: number; left: number };
+    boxSpacing?: number | { horizontal: number; vertical: number };
+    targetRowHeight?: number;
+    targetRowHeightTolerance?: number;
+    maxNumRows?: number;
+    forceAspectRatio?: boolean | number;
+    showWidows?: boolean;
+    fullWidthBreakoutRowCadence?: boolean | number;
+    widowLayoutStyle?: 'left' | 'center' | 'justify';
+  }
+
+  interface Box {
+    aspectRatio: number;
+    top: number;
+    left: number;
+    width: number;
+    height: number;
+    forcedAspectRatio?: boolean;
+  }
+
+  interface JustifiedLayoutResult {
+    containerHeight: number;
+    widowCount: number;
+    boxes: Box[];
+  }
+
+  type InputItem = number | { width: number; height: number };
+
+  function justifiedLayout(
+    input: InputItem[],
+    options?: JustifiedLayoutOptions
+  ): JustifiedLayoutResult;
+
+  export = justifiedLayout;
+}

frontend/src/types/theme.types.ts

@@ -15,7 +15,7 @@ export interface GalleryLayoutSettings {
   };
   
   // Masonry specific
-  masonryMode?: 'columns' | 'rows'; // columns = Pinterest-style, rows = Google Photos-style
+  masonryMode?: 'columns' | 'rows' | 'flickr' | 'justified'; // columns = Pinterest-style, rows = custom rows, flickr = Flickr justified-layout, justified = react-photo-album (Google Photos style)
   masonryGutter?: number;
   masonryRowHeight?: number; // Target row height for rows mode (150-400)
   masonryLastRowBehavior?: 'justify' | 'left' | 'center'; // How to align incomplete last row