feat: photography features & image optimizations

- Hero carousel: gallery.yaml hero accepts single UUID or array, crossfade component
- Full-bleed single albums: subpages with 1 album skip grid, render photos directly
- EXIF on hover: camera/lens/focal length overlay on grid items (toggle via exifOnHover)
- Customizable grid: columns/gap/aspectRatio/layout (masonry|uniform) via gallery.yaml
- Per-subpage grid overrides: each subpage can override global grid config
- True masonry: per-image aspect ratios from EXIF dimensions
- next/image migration: homepage hero, album covers, grid thumbnails, about portrait
- ThumbHash blur placeholders and dominant color backgrounds
- Custom next/image loader via image proxy with width/quality params
- Lightbox fade-in transition with dominant color background
- Password-protected subpages, health check, rate limiting, OG images

lib/urls.ts

@@ -4,6 +4,8 @@
  */
 
 import { encodeAssetId } from './tokens';
+import { thumbHashToBlurDataUrl, thumbHashToDominantHex } from './thumbhash';
+import type { ImmichAsset } from './immich';
 
 /**
  * Generate a public image proxy URL for an asset.
@@ -18,3 +20,63 @@ export function imageUrl(assetId: string, size: 'thumbnail' | 'preview' | 'origi
 export function exifUrl(assetId: string): string {
     return `/api/exif/${encodeAssetId(assetId)}`;
 }
+
+/**
+ * Placeholder data derived from an asset's ThumbHash.
+ */
+export interface PlaceholderData {
+    blurDataURL: string;
+    dominantColor: string;
+}
+
+/**
+ * Generate blur placeholder and dominant color from an asset's ThumbHash.
+ * Returns null if the asset has no ThumbHash.
+ */
+export function assetPlaceholder(asset: Pick<ImmichAsset, 'thumbhash'>): PlaceholderData | null {
+    if (!asset.thumbhash) return null;
+    try {
+        return {
+            blurDataURL: thumbHashToBlurDataUrl(asset.thumbhash),
+            dominantColor: thumbHashToDominantHex(asset.thumbhash),
+        };
+    } catch {
+        return null;
+    }
+}
+
+/**
+ * Compact EXIF summary for hover overlays.
+ */
+export interface ExifSummary {
+    camera?: string;
+    lens?: string;
+    focalLength?: string;
+}
+
+/**
+ * Extract a compact EXIF summary from an asset's exifInfo.
+ * Returns undefined if no relevant EXIF data is available.
+ */
+export function assetExifSummary(asset: Pick<ImmichAsset, 'exifInfo'>): ExifSummary | undefined {
+    const exif = asset.exifInfo;
+    if (!exif) return undefined;
+
+    const camera = exif.model || undefined;
+    const lens = exif.lensModel || undefined;
+    const focalLength = exif.focalLength ? `${exif.focalLength}mm` : undefined;
+
+    if (!camera && !lens && !focalLength) return undefined;
+    return { camera, lens, focalLength };
+}
+
+/**
+ * Compute the natural aspect ratio (width / height) from EXIF dimensions.
+ * Returns undefined if dimensions are not available.
+ */
+export function assetAspectRatio(asset: Pick<ImmichAsset, 'exifInfo'>): number | undefined {
+    const w = asset.exifInfo?.exifImageWidth;
+    const h = asset.exifInfo?.exifImageHeight;
+    if (w && h && h > 0) return w / h;
+    return undefined;
+}