feat: add a base map view tab

[oxgr]

Adds a base map view tab with a simple working map to build upon.

Using the GeoJSON format helps maintain a consistent & expected shape with some nice helper functions from Leaflet, but I'm not too sure how best to pass the Property objects from Django to Leaflet.

Currently using the existing Property JSON endpoint and manually parsing as GeoJSON.FeatureCollection in frontend to keep endpoints consistent while we figure out pagination.

Another option is to use djgeojson.GeoJsonLayerView to do this for us in backend, but not sure if it's too soon i.e. a lot to be adapted once pagination is sorted.

Related to #5

Type of change:

• [ ] Bug fix (change which fixes an issue).
• [x] New feature (change which adds functionality).
• [ ] Changes to models (requires making migrations).
• [ ] Documentation change.

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What's Changed:

• add a map view with a corresponding tab in the menu
• placeholder controls
• popup with property and harvest details

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Affected URLs:

• 127.0.0.1:8000/calendar/
• 127.0.0.1:8000/harvest/
• 127.0.0.1:8000/detailed_views/property/*

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Checklist:

• [x] My code follows the style guidelines of this project.
• [ ] I have performed a self-review of my own code.
• [x] I have commented my code, particularly in hard-to-understand areas.
• [ ] I have made corresponding changes to the documentation.
• [x] My changes generate no new warnings.
• [ ] New and existing unit tests pass locally with my changes.