docs: update README, CHANGELOG for slides/ restructure and binary refactor

- README.md: add slides/ directory, src/bin/slides_test.rs, src/lib.rs
  to project tree; add slides_test usage example
- README_en.md: same changes in English
- CHANGELOG.md: add v4.0.5 entry (slide migration, slides_test, rsync
  progress refactor, auto-install CLI output, edit dialog fixes)
- CHANGELOG_en.md: same in English

README_en.md

@@ -31,6 +31,10 @@ cargo run --release -- --demo
 
 # Automatic installation (with answer file)
 sudo cargo run --release -- --auto-install answer.toml
+
+# Slideshow test (standalone window, no root required)
+cargo run --bin slides_test [desktop] [lang]
+# E.g.: cargo run --bin slides_test xfce en
 ```
 
 ## Project Structure
@@ -38,9 +42,12 @@ sudo cargo run --release -- --auto-install answer.toml
 ```
 ├── src/
 │   ├── main.rs              # Entry point, eframe App, GUI layout
+│   ├── lib.rs               # Library root (reserved for future DLL structure)
 │   ├── installer.rs         # InstallerStep trait, GlobalState, WelcomeStep
 │   ├── funct.rs             # Shared UI helpers (form fields, language selector)
 │   ├── branding.rs          # Branding.toml loader (logo, slides, theme, OEM)
+│   ├── bin/
+│   │   └── slides_test.rs   # Standalone slideshow test binary
 │   ├── ui/
 │   │   ├── theme.rs         # Colors, fonts, Visuals, section_heading, error/warning/success boxes
 │   │   ├── buttons.rs       # Gradient buttons (primary, secondary, danger, etc.)
@@ -68,10 +75,14 @@ sudo cargo run --release -- --auto-install answer.toml
 ├── locales/
 │   ├── tr.toml              # Turkish translations
 │   └── en.toml              # English translations
+├── slides/
+│   ├── img/                 # Slide images (PNG)
+│   ├── slides_tr.toml       # Turkish slide content
+│   └── slides_en.toml       # English slide content
 ├── assets/
 │   ├── icons/               # UI icons (YALI_icon_LIGHT.svg, language-icon.svg, etc.)
 │   ├── flags/               # Country flags (~250 SVG)
-│   └── *.png                # Slide and logo images
+│   └── pisi-logo-*.png      # Distribution logos (branding `[general]`)
 ├── branding.toml            # Default branding configuration
 ├── branding_en.toml         # English branding
 ├── branding_tr.toml         # Turkish branding