docs: ship the acadrust MPL-2.0 notice, license text and local patch

The deployed site serves a .wasm with acadrust compiled into it, and our
vendored copy carries one modified MPL file
(src/io/dwg/dwg_stream_readers/object_reader/entities.rs, the read_mesh
array-count bounds fix). That is Executable Form distribution of modified
Covered Software, so MPL-2.0 3.2 requires the Source Code Form to be
available and recipients to be told how to get it. Nothing shipped said
so: no license text, no notice, no obtainable source - the upstream
mirror repos are private.

Add THIRD-PARTY-NOTICES.md plus public/licenses/ (MPL-2.0 text, the
read_mesh patch against the pristine 0.4.1 crate, and a served copy of
the notice), and link them from the page so recipients can actually find
them. Original crate download plus the patch reproduces the exact source
compiled into the wasm.

MPL does not require upstreaming, and the lineweight work did not touch
any MPL file - dwg-wasm/src/lib.rs is our MIT wrapper. docs/license-mpl2-
acadrust.md records the analysis and the checklist for future changes.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

index.html

@@ -275,6 +275,12 @@
       코드: <code>src/main.ts</code> ·
       지도: <a href="/docs/modules-dwg-dxf.html" target="_blank">docs/modules-dwg-dxf.html</a>
     </p>
+    <!-- MPL-2.0 §3.2(b): recipients of the wasm must be told where the
+         acadrust source (with our local patch) can be obtained. -->
+    <p style="margin:6px 0 0">
+      오픈소스 고지: <a href="/licenses/THIRD-PARTY-NOTICES.md" target="_blank">THIRD-PARTY-NOTICES</a>
+      (acadrust · MPL-2.0 · <a href="/licenses/acadrust-0.4.1-read_mesh.patch" target="_blank">local patch</a>)
+    </p>
   </aside>
 
   <script type="module" src="/src/main.ts"></script>