ifcviewer: preset-driven nav mouse bindings + a "Web" preset (desktop + web)

Make orbit/pan/select mouse bindings pure data owned by ViewportCore so both
hosts and every preset share one source of truth, and add a "Web" preset. This
rounds out the matrix: the desktop gains a web-style scheme and the web inherits
all presets, with no per-platform hardcoding.

- Core: NavBindings { orbit, pan, select button + modifier } + setNavPreset
  ("blender" default | "rhino" | "revit" | "web") + navBindings(). Select is
  preset-driven too (was hardcoded LMB) so "web" moves it to RMB. web = orbit
  LMB, pan MMB, select RMB (LMB drag orbits with no click/drag ambiguity; RMB
  click-selects / drag-marquees). NavMod uses "Plain" not "None" (X11 #defines
  None to 0L).
- Desktop ViewportWindow: applyNavPreset sources the core table (mapped to Qt);
  marquee-arm / single-pick dispatch keys off select_button_. Default stays
  blender → no behaviour change.
- Desktop config: AppSettings::NavPreset gains Web + navPresetName(); the
  Settings dialog lists it. This also FIXES a pre-existing gap — the preset combo
  was persisted but never applied (only WGPU_NAV_PRESET env worked). MainWindow
  now applies the persisted preset at startup (env override still wins) and live
  on navPresetChanged, so all four presets actually work from the dialog.
- Web main_web: classifyPress routes the pressed button through navBindings()
  (orbit/pan/select), defaulting to the "web" preset; context menu already
  suppressed so RMB is free.

Tests: setNavPreset table (Catch2, 123 total); web smoke select tests use RMB.
BonsaiViewer builds; 9/9 web smoke.

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

src/ifcviewer/AppSettings.cpp

@@ -186,6 +186,16 @@ AppSettings::NavPreset AppSettings::navPreset() const {
     return nav_preset_;
 }
 
+const char* AppSettings::navPresetName(NavPreset preset) {
+    switch (preset) {
+        case NavPreset::Rhino:   return "rhino";
+        case NavPreset::Revit:   return "revit";
+        case NavPreset::Web:     return "web";
+        case NavPreset::Blender: break;
+    }
+    return "blender";
+}
+
 void AppSettings::setNavPreset(NavPreset value) {
     if (nav_preset_ == value) return;
     nav_preset_ = value;
@@ -220,7 +230,7 @@ void AppSettings::load() {
                                        static_cast<int>(NavPreset::Blender)).toInt();
         // Clamp to known values so a stale config doesn't drop us into
         // an undefined preset slot.
-        if (raw < 0 || raw > static_cast<int>(NavPreset::Revit)) {
+        if (raw < 0 || raw > static_cast<int>(NavPreset::Web)) {
             nav_preset_ = NavPreset::Blender;
         } else {
             nav_preset_ = static_cast<NavPreset>(raw);