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

app/api/health/route.ts

@@ -0,0 +1,26 @@
+/**
+ * Health check endpoint — reports app and Immich connectivity status.
+ * Used by Docker HEALTHCHECK, monitoring tools, and load balancers.
+ *
+ * GET /api/health → { status, immich, uptime }
+ */
+
+import { NextResponse } from 'next/server';
+import { immich } from '@/lib/immich';
+
+const startTime = Date.now();
+
+export async function GET() {
+    const immichOk = await immich.ping();
+
+    const body = {
+        status: immichOk ? 'ok' : 'degraded',
+        immich: immichOk ? 'connected' : 'unreachable',
+        uptime: Math.floor((Date.now() - startTime) / 1000),
+    };
+
+    return NextResponse.json(body, {
+        status: immichOk ? 200 : 503,
+        headers: { 'Cache-Control': 'no-store' },
+    });
+}