feat(ui): replace app-menu logo with a quick-access file toolbar

Remove the OCS-logo button and the dropdown menu it opened; the top strip
now shows direct New / Open / Save / Save As / Print buttons ahead of the
undo/redo controls. Drop the HELP and OPTIONS commands (HELP dumped text to
the command line, OPTIONS aliased the drafting-settings popup).

The app-menu overlay is gone, so its rendering code, MENU_ITEMS, four dead
messages, and the LOGO_RED / GEAR / HELP assets are removed. The recents
list it held is the only survivor — moved into OpenCADStudio.recent_files
via a new app/recent.rs, backing the Start page's Recent Documents panel.

Quick-access icons are redrawn in a cleaner style (file-plus, folder-open,
device-floppy, file-export, printer) and tinted light so they read on the
dark strip; FOLDER / DOC keep their old glyphs for the file browser.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/recent.rs

@@ -0,0 +1,75 @@
+//! Persistent recent-files store backing the Start page's Recent Documents
+//! panel. Stored as plain text on disk (one path per line, newest first) next
+//! to the other per-user config, so no serialization crate is pulled in just
+//! for this.
+
+use super::OpenCADStudio;
+use std::path::{Path, PathBuf};
+
+impl OpenCADStudio {
+    /// Record a freshly opened file at the top of the recents list.
+    pub(super) fn push_recent(&mut self, path: PathBuf) {
+        self.recent_files.retain(|r| r != &path);
+        self.recent_files.insert(0, path);
+        self.recent_files.truncate(20);
+        // Best-effort persist; silent on failure (read-only home, full disk).
+        let _ = save_recents(&self.recent_files);
+    }
+
+    /// Drop a path from the recents list (manual removal from the Start page).
+    pub(super) fn remove_recent(&mut self, path: &Path) {
+        self.recent_files.retain(|r| r.as_path() != path);
+        let _ = save_recents(&self.recent_files);
+    }
+}
+
+/// Rehydrate the recents list from disk. Call once at app boot.
+pub(super) fn load_recent_files() -> Vec<PathBuf> {
+    let Some(path) = recents_file_path() else {
+        return vec![];
+    };
+    let Ok(body) = std::fs::read_to_string(path) else {
+        return vec![];
+    };
+    body.lines()
+        .filter(|l| !l.trim().is_empty())
+        .map(PathBuf::from)
+        .collect()
+}
+
+fn recents_file_path() -> Option<PathBuf> {
+    let base: PathBuf = if cfg!(target_os = "windows") {
+        std::env::var_os("APPDATA").map(PathBuf::from)?
+    } else if cfg!(target_os = "macos") {
+        let home = std::env::var_os("HOME")?;
+        let mut p = PathBuf::from(home);
+        p.push("Library");
+        p.push("Application Support");
+        p
+    } else if let Some(d) = std::env::var_os("XDG_CONFIG_HOME") {
+        PathBuf::from(d)
+    } else {
+        let home = std::env::var_os("HOME")?;
+        let mut p = PathBuf::from(home);
+        p.push(".config");
+        p
+    };
+    let mut p = base;
+    p.push("OpenCADStudio");
+    Some(p.join("recent.txt"))
+}
+
+fn save_recents(list: &[PathBuf]) -> std::io::Result<()> {
+    let Some(path) = recents_file_path() else {
+        return Ok(());
+    };
+    if let Some(dir) = path.parent() {
+        std::fs::create_dir_all(dir)?;
+    }
+    let body: String = list
+        .iter()
+        .map(|p| p.to_string_lossy().into_owned())
+        .collect::<Vec<_>>()
+        .join("\n");
+    std::fs::write(path, body)
+}