feat: IFC → Pascal converter (package + app)

Brings the IFC-to-Pascal converter into the monorepo as a pure-logic
package plus a Next.js app, replacing the standalone repo that consumed
published @pascal-app/* packages (and drifted from their schemas).

packages/ifc-converter — pure conversion. Parses IFC via web-ifc and
maps elements onto @pascal-app/core node schemas (workspace-linked, so
no more version drift). Builds doors/windows, walls, slabs, columns,
roofs, stairs, sites/buildings/levels. Validates each node via the real
Zod schemas at build time (tryParse) and strips undefined metadata.

apps/ifc-converter — the UI: drop zone, example picker, element search,
JSON download, and a 3D preview rendered through the real
@pascal-app/viewer (registry bootstrap + read-only scene) with a custom
toolbar (camera/level/wall/grid/theme), level selector with
camera-focus, auto-fit, and selection bridged to an inspector.

Conversion specifics worth noting:
- Door/window vertical centering (height/2; windows + sill).
- Nearest-wall hosting fallback for files lacking IFCRELFILLSELEMENT,
  preferring walls long enough to contain the opening and clamping the
  along-wall position so cutouts can't overflow and break wall CSG.
- Plain IFCWALL (Brep/mapped geometry) falls back to default
  height/thickness instead of collapsing to zero-height slivers.
- Columns convert as plain structural shafts (no decorative
  base/capital) sized from the IFC profile.
- Beams + items are skipped for now (no Pascal beam type; items need a
  catalog asset) — counted in the conversion summary.

Large example IFCs are fetched from a public bucket at runtime; the four
small ones are committed. web-ifc.wasm is copied into public/ on
install/dev/build. README flags early-alpha + invites contributions.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/ifc-converter/public/.gitignore

@@ -0,0 +1,5 @@
+# Copied from node_modules/web-ifc/ by scripts/copy-web-ifc-wasm.mjs
+# (runs on postinstall / predev / prebuild).
+web-ifc.wasm
+web-ifc-mt.wasm
+web-ifc-node.wasm