refactor: move all dialog UIs to dedicated files under src/ui/

Each dialog window (Page Setup, DimStyle, TextStyle, TableStyle,
MLineStyle, PlotStyle, Layout Manager, Shortcuts) is now a proper
window-filling layout in its own src/ui/<dialog>.rs file.

Pattern: toolbar strip at top + vertical separator + scrollable
content filling the rest — no modal card, no backdrop, no stack[].
Matches the existing Layer Manager window pattern.

Removed ~1600 lines of old overlay functions from view.rs.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/ui/mod.rs

@@ -4,12 +4,20 @@ pub const ROW_H: f32 = 26.0;
 
 pub mod app_menu;
 pub mod command_line;
+pub mod dimstyle;
 pub mod layers;
+pub mod layout_manager;
+pub mod mlstyle;
 pub mod overlay;
+pub mod page_setup;
+pub mod plotstyle;
 pub mod properties;
 pub mod ribbon;
+pub mod shortcuts;
 pub mod snap_popup;
 pub mod statusbar;
+pub mod tablestyle;
+pub mod textstyle;
 
 pub use app_menu::AppMenu;
 pub use command_line::CommandLine;