fix: catch sharp errors in ensureLocalThumbnail and fall back to original

Sharp throws on unsupported formats (HEIC, corrupt files, etc.) and the
error was propagated outside the try/catch, crashing the server. Moved the
mkdir + sharp pipeline inside the catch block so any failure returns null
and streamPhoto falls through to serving the original file.

server/src/services/memories/thumbnailService.ts

@@ -27,7 +27,6 @@ export async function ensureLocalThumbnail(
       const meta = await sharp(thumbAbs).metadata()
       return { thumbnailRelPath: thumbRel, width: meta.width ?? 0, height: meta.height ?? 0 }
     }
-  } catch { /* regenerate */ }
 
     await fs.mkdir(path.dirname(thumbAbs), { recursive: true })
     await sharp(originalAbs)
@@ -37,4 +36,8 @@ export async function ensureLocalThumbnail(
       .toFile(thumbAbs)
     const meta = await sharp(thumbAbs).metadata()
     return { thumbnailRelPath: thumbRel, width: meta.width ?? 0, height: meta.height ?? 0 }
+  } catch {
+    // Unsupported format, corrupt file, etc. — fall back to original in caller.
+    return null
+  }
 }