feature: PDF and PDF thumbnails and refresh UI

- Implement PDF and PDF thumbnail generation with incremental loading
- Add UI refresh mechanism (tick counter + RefreshView message)
- Improve fl! macro with named parameters
- Clean up code organization (mod.rs: wiring, model.rs: state only)

i18n/en/noctua.ftl

@@ -1,55 +1,92 @@
 # SPDX-License-Identifier: GPL-3.0-or-later
 # i18n/en/noctua.ftl
 #
-# Localization strings for Noctua's user interface (English).
+# Localization strings for Noctua (English).
+# Usage: fl!("message-id", arg1, arg2, ...)
+#
+# Positional arguments ($1, $2, ...) are used for variable content.
 
 
-## Application metadata
+## Application
 noctua-app-name = Noctua
-noctua-app-description = A wise document and image viewer for the COSMIC™ desktop
+noctua-app-description = A document and image viewer for the COSMIC desktop
+
 
 ## Main window
 window-title = { $filename ->
-    *[none] Noctua
-    *[some] { $filename } — Noctua
+    [none] Noctua
+   *[some] { $filename } — Noctua
 }
 
+
 ## Menu entries
 menu-file-open = Open…
 menu-file-quit = Quit
 menu-view-zoom-in = Zoom In
 menu-view-zoom-out = Zoom Out
 menu-view-zoom-reset = Reset Zoom
+menu-view-zoom-fit = Fit to Window
 menu-view-flip-horizontal = Flip Horizontally
 menu-view-flip-vertical = Flip Vertically
 menu-view-rotate-cw = Rotate Clockwise
 menu-view-rotate-ccw = Rotate Counter-Clockwise
 
-## Placeholders / empty states
+
+## Tooltips (for buttons and icons)
+tooltip-nav-previous = Previous document
+tooltip-nav-next = Next document
+tooltip-nav-toggle = Toggle navigation panel
+tooltip-zoom-in = Zoom in
+tooltip-zoom-out = Zoom out
+tooltip-zoom-fit = Fit to window
+tooltip-rotate-ccw = Rotate counter-clockwise
+tooltip-rotate-cw = Rotate clockwise
+tooltip-flip-horizontal = Flip horizontally
+tooltip-flip-vertical = Flip vertically
+tooltip-info-panel = Toggle info panel
+
+
+## Footer / Status bar
+status-zoom-fit = Fit
+status-zoom-percent = { $percent }%
+status-doc-dimensions = { $width } × { $height }
+status-nav-position = { $current } / { $total }
+status-separator =  | 
+
+
+## Placeholders / Empty states
 no-document = No document loaded
 
+
 ## Labels
-zoom = Zoom
-tools = Tools
-crop = Crop
-scale = Scale
+label-zoom = Zoom
+label-tools = Tools
+label-crop = Crop
+label-scale = Scale
+label-page = Page
+label-pages = Pages
+
+
+## Loading states
+loading-metadata = Loading metadata…
+loading-thumbnails = Loading { $current } / { $total }…
+
 
 ## Error messages
-error-failed-to-open = Failed to open "{ $path }".
-error-unsupported-format = Unsupported file format.
+error-failed-to-open = Failed to open "{ $path }"
+error-unsupported-format = Unsupported file format
+error-no-image-loaded = No image loaded
+
 
 ## Properties panel
 panel-properties = Properties
 panel-actions = Actions
+
 meta-section-file = File Information
 meta-section-exif = Camera Information
+meta-section-image = Image Information
 
-## Action buttons
-action-set-wallpaper = Set as Wallpaper
-action-open-with = Open With…
-action-show-in-folder = Show in Folder
-
-## Basic metadata
+## File metadata
 meta-filename = Name
 meta-format = Format
 meta-dimensions = Dimensions
@@ -59,14 +96,26 @@ meta-path = Path
 meta-pages = Pages
 meta-current-page = Current Page
 
+## Image metadata
+meta-width = Width
+meta-height = Height
+meta-depth = Bit Depth
+
 ## EXIF metadata
 meta-camera = Camera
 meta-datetime = Date Taken
 meta-exposure = Exposure
 meta-aperture = Aperture
-meta-iso = ISO
+meta-iso = ISO { $iso }
 meta-focal = Focal Length
 meta-gps = GPS Location
 
-## States
-loading-metadata = Loading...
+## Action buttons
+action-set-wallpaper = Set as Wallpaper
+action-open-with = Open With…
+action-show-in-folder = Show in Folder
+
+
+## Navigation panel (thumbnails)
+nav-panel-title = Pages
+nav-panel-loading = Loading { $current } / { $total }…