feat: web automation wrapper (#1349), DATALINK table on web, System theme; honest decode accounting

Ported from 2c38de53 (#1717). Main already carries the hatch PDF draw
order fix (#1345), the numeric set_properties compare (#1348) and the
web open from bytes, so those parts stay out; what remains:

#1349 — window.ocsControl.ready/request promise wrapper with an
ocs-ready event (web/ocs-control.js, loaded by the web page), and the
startup donation prompt is suppressed once a control request is seen
(opt-in pre-boot via localStorage["opencadstudio.automation"] = "1").
docs/automation/web.md documents both. The control protocol stays at 1.

DATALINK CSV-to-table works on web (picker + bytes through the session
registry — was std::fs, silently dead); COLORSCHEME accepts System
(prefers-color-scheme on web, AppsUseLightTheme on Windows).

Decode accounting, made honest per the fix-of-fix review: into_rgba8
allocates the RGBA destination while the native buffer is alive for
every non-Rgba8 layout (L8 5, La8 6, Rgb8 7, L16 6, La16 8 B/px
peaks — the formula now says so), GIF bills the screen+frame
coexistence at 8 B/px, and TIFF drops the 3x multipliers both ways —
tiff 0.11 splits the given budget between frame and scratch (a total
ceiling), so the old double-billing refused honest 16-bit GeoTIFFs
~2.25x early while admitting hostile chunk transients at 3x.

(cherry picked from commit 2c38de53)

src/app/update/file.rs

@@ -1348,6 +1348,14 @@ impl OpenCADStudio {
     pub(in crate::app) fn apply_config(&mut self, cfg: crate::app::config::AppConfig) {
         self.apply_settings(&cfg.settings);
         self.ui_theme = cfg.theme.clone();
+        // A saved `System` scheme re-resolves at boot: the stored palette is
+        // whatever the last resolution produced, so refresh it alongside the
+        // live theme (COLORSCHEME SYSTEM documents this boot-time read).
+        if self.ui_theme.name.eq_ignore_ascii_case("System") {
+            self.ui_theme.palette = crate::app::config::UiThemePalette::from_iced(
+                crate::app::config::resolve_system_theme().seed(),
+            );
+        }
         self.active_theme = self.ui_theme.to_iced();
         self.theme_color_inputs = self.ui_theme.palette.hex_values();
         self.model_space = cfg.model_space;

src/app/update/mod.rs

@@ -2964,6 +2964,12 @@ impl OpenCADStudio {
             #[cfg(target_arch = "wasm32")]
             Message::ScriptFilePicked(None) => Task::none(),
 
+            // Web DATALINK: the picked .csv's bytes arrived — register them
+            // as the link's in-session source, then run the same table-insert
+            // path the native typed-path command feeds.
+            #[cfg(target_arch = "wasm32")]
+            Message::DataLinkCsvPicked(picked) => self.on_datalink_csv_picked(picked),
+
             // Web CENTERLTYPEFILE: the picked .lin/.dnl file's text arrived —
             // load its linetypes, then record the setting under the file's
             // name (the native command reads the typed path inside