chore: rename H7CAD to Open CAD Studio

Joining the OpenAEC Foundation (open-aec.com). Crate/struct become
OpenCADStudio, user-facing strings use the spaced "Open CAD Studio"
form, repo URLs point to HakanSeven12/open-cad-studio. Logo (window
icon + assets/logo.svg) redrawn with OCS initials. Drop examples/
binaries — unused.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/ui/about.rs

@@ -57,7 +57,7 @@ pub fn view_window<'a>() -> Element<'a, Message> {
 
     let logo = container(
         column![
-            text("H7CAD").size(32).color(ACCENT),
+            text("Open CAD Studio").size(32).color(ACCENT),
             text("CAD application for Architecture & Engineering")
                 .size(11)
                 .color(DIM),