fix(pdf): follow-ups to the PDF underlay merge

- Pin cadcodec upstream at d290dbe (the merged underlay change) and
  cadkernel at 4134ae3, which follows it; drop the fork patch, move the
  plugin-API and web-worker crates and the Python plugin lock to the same
  codec so one copy is built.
- "Import as block" with raster images left IMAGE entities without an
  image definition: block definition now creates it like add_entity does,
  through one shared helper.
- The three preview outlines (attach frame, clip boundary, import area)
  stay f64 instead of casting world points to f32.
- Page size / total / PDF scale entries use the catalog's positional
  placeholder; the bare {name} form failed to format in 20 locales.
- The Underlay Layers bulb is the SVG layer icon, not a text glyph.
- PDF dialogs use the shared dialog buttons and radios.
- Options opened from a PDF dialog clears its saved state on return.
- Paper-space underlay background reuses the model block handle already
  resolved; dead `let _ = i` lines and a misplaced doc comment removed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

plugins/opencad-python/Cargo.lock

@@ -5,7 +5,7 @@ version = 4
 [[package]]
 name = "acadrust"
 version = "0.5.5"
-source = "git+https://github.com/HakanSeven12/cadcodec.git?rev=dd1d7bf#dd1d7bfe03f4e733d351c0396e2cf82ae9df957d"
+source = "git+https://github.com/HakanSeven12/cadcodec.git?rev=d290dbe#d290dbe1712666d83dfd0fc63341ee3246f8de76"
 dependencies = [
  "ahash 0.8.12",
  "anyhow",