ifcviewer-web: navigation parity — view all, XYZ views, ortho, zoom-to-selected

The camera math already lived in the shared ViewportCore; the desktop just
bound keys to it. The web build had no keyboard handler and no camera UI, so
none of it was reachable. Wire it up (Tier 1 + 2 of nav parity; fly mode is a
separate follow-up).

Shared core:
- setStandardView(StandardView) — named Front/Back/Left/Right/Top/Bottom wrapper
  over setStandardView(yaw,pitch), so the axis→angle mapping lives in one place.
- frameSelection() — lifts the desktop's "union selected AABBs → frameAabb(1.30)"
  focus logic out of ViewportWindow into the core. Desktop's focusOnSelectedObject
  and the X/Y/Z hotkeys now call these (DRY, behaviour unchanged).

Web:
- main_web gains a keydown handler matching the desktop bindings — Home=view all,
  F=zoom to selected, P=ortho toggle, X/Y/Z (+Shift=negative)=standard views —
  plus exported entry points (view_all_c / frame_selection_c / toggle_projection_c
  / projection_is_ortho_c / standard_view_c) for the toolbar.
- shell.html adds a bottom nav toolbar (Fit / Focus / Persp-Ortho / the six views)
  with the hotkeys in tooltips; the ortho button reflects state.

Verified: Z key and Front button both move the camera, ortho toggles render +
label, zero GPU errors; 111/111 unit + 6/6 web smoke pass.

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

src/ifcviewer/ViewportCore.h

@@ -185,6 +185,19 @@ public:
                    float dist, float yaw_deg, float pitch_deg);
     void setStandardView(float yaw_deg, float pitch_deg);
 
+    // Named axis-aligned views. Front/Back/Left/Right pin yaw at 0/180/270/90
+    // (pitch 0); Top/Bottom pin pitch at ±90° and keep the current yaw. Wraps
+    // setStandardView(yaw,pitch) so the mapping lives in one place (shared by
+    // the desktop hotkeys and the web toolbar/keys).
+    enum class StandardView { Front, Back, Left, Right, Top, Bottom };
+    void setStandardView(StandardView view);
+
+    // Frame the current selection: union the selected objects' world AABBs and
+    // fit the camera to them (same 1.30 padding as the desktop "F" hotkey).
+    // No-op with an empty selection or no resolvable AABBs; returns whether it
+    // framed anything. Uses the shared selection + computeObjectAabb/frameAabb.
+    bool frameSelection();
+
     // ---- Incremental orbit navigation ---------------------------------------
     //
     // Pixel-delta camera moves, shared by every host (Qt desktop + web).