Attempt to calculate annotation offsets

There are clear issues remaining with this approach.

The wallabag-given 'start' and 'end' fields do _not_ just point to the
n-th paragraph all the time (like I thought) but actually represent a
beautifulsoup4 like tree descent.

So:  `p_start_match = re.match(r"/p\[(\d+)\]", annot["ranges"][0]["start"])`
will fail on any annotation not just at the n-th paragraph.

Instead we should see how we can move this tree into the beautifulsoup4
parser and make use of wallabag already having done the work for us?

pyproject.toml

@@ -5,12 +5,12 @@ description = "Add your description here"
 readme = "README.md"
 requires-python = ">=3.13"
 dependencies = [
+    "beautifulsoup4>=4.13.3",
+    "lxml>=5.3.1",
+    "requests>=2.32.3",
     # REQUIRED FOR CURRENT SHAARLI2HOARDER IMPLEMENTATION ONLY
-    # "beautifulsoup4>=4.13.3",
     # "netscape-bookmarks-file-parser",
     # "pyjwt>=2.10.1",
-    # "requests>=2.32.3",
-    "requests>=2.32.3",
 ]
 
 [tool.pyright]