feat(ui): persist window state and clarify transfer telemetry

- Persist bounded logical main-window geometry with work-area-safe startup restoration.
- Persist the Folders collapse preference in SQLite with guarded legacy localStorage migration.
- Keep media transfer telemetry truthful and compact the transfer controls across locales.
- Add bridge, presentation, persistence, geometry, and configuration regression coverage.

src-tauri/src/window_geometry.rs

@@ -0,0 +1,97 @@
+use crate::ipc::MainWindowSize;
+
+pub const MAIN_WINDOW_DEFAULT_WIDTH: u32 = 1280;
+pub const MAIN_WINDOW_DEFAULT_HEIGHT: u32 = 800;
+pub const MAIN_WINDOW_MIN_WIDTH: u32 = 960;
+pub const MAIN_WINDOW_MIN_HEIGHT: u32 = 640;
+pub const MAIN_WINDOW_MAX_WIDTH: u32 = 16_384;
+pub const MAIN_WINDOW_MAX_HEIGHT: u32 = 16_384;
+
+pub fn default_main_window_size() -> MainWindowSize {
+    MainWindowSize {
+        width: MAIN_WINDOW_DEFAULT_WIDTH,
+        height: MAIN_WINDOW_DEFAULT_HEIGHT,
+    }
+}
+
+pub fn normalize_main_window_size(size: Option<&MainWindowSize>) -> Option<MainWindowSize> {
+    let size = size?;
+    if size.width < MAIN_WINDOW_MIN_WIDTH
+        || size.height < MAIN_WINDOW_MIN_HEIGHT
+        || size.width > MAIN_WINDOW_MAX_WIDTH
+        || size.height > MAIN_WINDOW_MAX_HEIGHT
+    {
+        return None;
+    }
+    Some(size.clone())
+}
+
+pub fn clamp_main_window_size(
+    size: MainWindowSize,
+    work_area_width: u32,
+    work_area_height: u32,
+) -> MainWindowSize {
+    let width_limit = work_area_width.max(MAIN_WINDOW_MIN_WIDTH);
+    let height_limit = work_area_height.max(MAIN_WINDOW_MIN_HEIGHT);
+    MainWindowSize {
+        width: size.width.min(width_limit),
+        height: size.height.min(height_limit),
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{
+        clamp_main_window_size, default_main_window_size, normalize_main_window_size,
+        MAIN_WINDOW_MIN_HEIGHT, MAIN_WINDOW_MIN_WIDTH,
+    };
+    use crate::ipc::MainWindowSize;
+
+    #[test]
+    fn default_size_matches_the_main_window_configuration() {
+        assert_eq!(default_main_window_size().width, 1280);
+        assert_eq!(default_main_window_size().height, 800);
+    }
+
+    #[test]
+    fn rejects_sizes_outside_the_persisted_bounds() {
+        assert!(normalize_main_window_size(Some(&MainWindowSize {
+            width: MAIN_WINDOW_MIN_WIDTH - 1,
+            height: 800,
+        }))
+        .is_none());
+        assert!(normalize_main_window_size(Some(&MainWindowSize {
+            width: 1280,
+            height: 16_385,
+        }))
+        .is_none());
+    }
+
+    #[test]
+    fn caps_a_valid_size_to_the_available_work_area() {
+        let clamped = clamp_main_window_size(
+            MainWindowSize {
+                width: 1600,
+                height: 1000,
+            },
+            1280,
+            720,
+        );
+        assert_eq!(clamped.width, 1280);
+        assert_eq!(clamped.height, 720);
+    }
+
+    #[test]
+    fn keeps_the_minimum_when_the_work_area_is_shorter_than_the_minimum() {
+        let clamped = clamp_main_window_size(
+            MainWindowSize {
+                width: 1280,
+                height: 800,
+            },
+            800,
+            500,
+        );
+        assert_eq!(clamped.width, MAIN_WINDOW_MIN_WIDTH);
+        assert_eq!(clamped.height, MAIN_WINDOW_MIN_HEIGHT);
+    }
+}