feat: improve PDF image extraction with caption-based labeling and fallback matching

- Enhance pdf_image_extractor with caption text extraction near images/tables
- Add figure/table type correction based on caption content
- Implement sequential numbering fallback for unmatched items
- Improve figure linking in pages with manifest ID matching and fallback strategies
- Remove docling dependency, add dev dependency group

pyproject.toml

@@ -19,7 +19,6 @@ dependencies = [
     "pymupdf>=1.25",
     "itsdangerous>=2.2.0",
     "bleach>=6.4.0",
-    "docling>=2.99.0",
 ]
 
 [project.optional-dependencies]
@@ -34,3 +33,9 @@ build-backend = "hatchling.build"
 
 [tool.hatch.build.targets.wheel]
 packages = ["app"]
+
+[dependency-groups]
+dev = [
+    "pytest>=9.0.3",
+    "pytest-asyncio>=1.4.0",
+]