wasm scan: keep page_count/finish exported after the add_page split

Splitting add_page into a #[wasm_bindgen] wrapper pair plus a plain
add_page_impl left page_count and finish inside the non-wasm_bindgen impl
block, so they stopped being exported to JS ("cur.conv.finish is not a
function"). Close the plain impl right after add_page_impl and put
page_count/finish back in a #[wasm_bindgen] impl block.

Refs #157

Signed-off-by: artiz <artem.kustikov@gmail.com>
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EY5KAiquN4YpVf2PXEQkVT

Author: artiz

crates/docling-wasm/src/scanned.rs

@@ -210,7 +210,10 @@ impl ScannedConverter {
             .push(assemble_page_with_tables(&page, regions, table_rows));
         Ok(())
     }
+}
 
+#[wasm_bindgen]
+impl ScannedConverter {
     /// Number of pages converted so far (progress display).
     pub fn page_count(&self) -> usize {
         self.pages.len()