Add photo frame idle mode and switch to Skylight-style theme

- After 5 min of no touch/motion, dashboard hides behind a fullscreen
  photo slideshow with centered time and date overlay
- Photos loaded from PHOTOS_PATH env var (defaults to ~/Pictures/dashboard)
  via IPC + file:// URLs; traversal-guarded, recursive up to 2 levels
- Motion or touch exits idle back to dashboard
- Theme repainted warm cream / sage / stone ink with Nunito font and
  rounded cards; dark tokens kept so component classes still resolve
- Adds PHOTO_FRAME.md with Samba cifs mount + systemd env instructions

electron/services/PhotoManager.ts

@@ -0,0 +1,53 @@
+import * as fs from 'fs';
+import * as path from 'path';
+
+const IMAGE_EXTS = new Set(['.jpg', '.jpeg', '.png', '.webp', '.gif', '.heic', '.heif']);
+
+/**
+ * Lists image files from the configured photos directory.
+ * Recurses one level deep so users can organise photos into subfolders.
+ */
+export class PhotoManager {
+  constructor(private photosDir: string) {}
+
+  setDir(dir: string): void {
+    this.photosDir = dir;
+  }
+
+  getDir(): string {
+    return this.photosDir;
+  }
+
+  list(): string[] {
+    if (!this.photosDir || !fs.existsSync(this.photosDir)) return [];
+    const files: string[] = [];
+    try {
+      this.walk(this.photosDir, files, 0);
+    } catch (err) {
+      console.error('PhotoManager: failed to list photos', err);
+    }
+    // Return paths relative to photosDir so the renderer can build photo:// URLs
+    return files.map((f) => path.relative(this.photosDir, f));
+  }
+
+  private walk(dir: string, out: string[], depth: number): void {
+    if (depth > 2) return;
+    for (const entry of fs.readdirSync(dir, { withFileTypes: true })) {
+      if (entry.name.startsWith('.')) continue;
+      const full = path.join(dir, entry.name);
+      if (entry.isDirectory()) {
+        this.walk(full, out, depth + 1);
+      } else if (entry.isFile() && IMAGE_EXTS.has(path.extname(entry.name).toLowerCase())) {
+        out.push(full);
+      }
+    }
+  }
+
+  resolve(relative: string): string | null {
+    if (!this.photosDir) return null;
+    const safe = path.normalize(relative).replace(/^(\.\.[\/\\])+/, '');
+    const full = path.join(this.photosDir, safe);
+    if (!full.startsWith(this.photosDir)) return null;
+    return full;
+  }
+}