QA: Cleanup centerline tagging with separate sidewalks

## Context

- To generate a good sidewalk network we need consistent data on sidewalks either on the centerline or mapped separately. Mixed data causes edge cases and problems and we want to clean up the data in OSM to avoid those.

## Goal

- This QA step should allow mappers to improve the sidewalk tagging on the centerline where it does not match the separate sidewalk data

Related but different: https://github.com/a-b-street/speedwalk/issues/15

## QA-Items

- Places where the centerline has a sidewalk-tagging other than "`separate`" and there is a separate geometry
- Places where the centerline has a sidewalk-tag `separate` but there is no separate geometry to be found

Note: There might be edge cases like separate geometries that the tool does not recognize but the centerline tagging is correct. A good workaround to resolves those in tags could be to allow `check_date:sidewalk(:SIDE)=DATE_STRING` ([Taginfo](https://taginfo.openstreetmap.org/search?q=check_date%3Asidewalk)) as an overwrite for the QA check.

## Workflow

Possible workflow…

This might be a good use case to edit right from Speedwalk since changes are pretty easy.
However, the tool needs to handle all the different sidewalk-tagging variation to do this, see https://github.com/openstreetmap/iD/pull/10935

The issue describes a QA tool for OpenStreetMap sidewalk tagging. Start by reviewing the related issue #15 and the linked iD pull request to understand sidewalk tagging variations. The tool likely needs to compare centerline tags with separate sidewalk geometries. Look at the existing codebase for how sidewalk data is currently processed and validated. 'Done' means the tool can identify mismatches and possibly allow in-app editing with a check_date override.

Written by the indexing model from the issue text.