feat: zoom percentage badge at bottom center (v1.7.1)

- Percentage shown between the prev/next buttons, together with the hover
  controls, on a translucent background.
- Value is the on-screen scale relative to the image's real pixel size
  (100% = 1:1); updated on wheel zoom, fill/fit toggle, image change and
  window resize.
- Pixel-size header parsing moved to lib/services/image_header.dart, shared
  with the settings file-properties panel.
- dist: 1.7.1 .deb replaces the tracked 1.7.0 package.

CHANGELOG.md

@@ -4,6 +4,19 @@ All notable changes to imajViewer are documented in this file.
 
 ## [Unreleased]
 
+## [1.7.1] - 2026-10-25
+
+### Added
+- Zoom percentage badge at the bottom center, between the previous/next buttons: shown
+  together with the hover controls, translucent background, live while wheeling
+  (100% = one image pixel per screen pixel), recomputed on fill/fit toggle, image
+  change and window resize.
+
+### Changed
+- Image header parsing (pixel size without decoding) moved from the viewer screen into
+  `lib/services/image_header.dart`; the settings file-properties panel and the zoom badge
+  use the same code.
+
 ## [1.7.0] - 2026-10-20
 
 ### Added