feat: Kisani UI overhaul — brand identity, gallery, visual polish

- Rename app to Kisani (CFBundleDisplayName, xcodeproj → Kisani.xcodeproj)
- BackupView: kisani. wordmark + SwiftUI-drawn server logo mark (no asset,
  adaptive ink/bg), 206pt progress ring with active-state glow, 4-page
  swipeable ring (progress/pending/failed/uploaded), 4-metric stats strip,
  friendly NAS card (Home Server label), hamburger → AppMenuView sheet
- GalleryView: new NAS + local photo grid with source picker chip, 3-col
  lazy grid, ThumbnailCache, sync-status dots (green = backed up)
- MainTabView: Browse tab → Gallery tab; tab bar uses ultraThinMaterial
  blur background (systemGray3 icons, 9.5pt labels)
- All app icon sizes regenerated from 1024pt source via sips
- LANMonitor: nasReachable Bool?, checkNASReachability(host:port:) TCP ping
- project.yml: photo library usage description updated to Kisani branding

Co-Authored-By: Kutesir <kutesir@provoc.ug>
Co-Authored-By: Sentry <sentry@provoc.ug>

Services/SFTPService.swift

@@ -80,6 +80,14 @@ final class SFTPService: NASTransferProtocol {
         }
     }
 
+    func downloadData(at remotePath: String) async throws -> Data {
+        guard let sftp else { throw BackupError.connectionFailed("Not connected") }
+        return try await sftp.withFile(filePath: remotePath, flags: [.read]) { file in
+            let buf = try await file.readAll()
+            return Data(buf.readableBytesView)
+        }
+    }
+
     func upload(localURL: URL, remotePath: String, progress: @escaping (Int64, Int64) -> Void) async throws {
         guard let sftp else { throw BackupError.connectionFailed("Not connected") }
         let filename = localURL.lastPathComponent