feat: add --no-text flag to conditionally disable text overlays on map posters

[fasaya]

This PR introduces a new --no-text command-line argument that allows users to generate map posters without any embedded text overlays. By default, maps are generated with the city, country, coordinates, and attribution text, but in some scenarios (e.g., when users want to use the maps as clean backgrounds or apply custom text in post-processing), a completely textless variant is preferred.

Changes Made:

• Added a --no-text argument flag to create_map_poster.py.
• Updated make_poster logic to accept a new show_text boolean parameter (derived from not args.no_text).
• Wrapped the rendering logic for the main title, subtitle, coordinates, divider line, and attribution within a conditional if show_text: block.
• Updated the testing suite in test/all_variations.sh to include a validation step for the new --no-text flag.
• Added flag documentation to the script's help menu.

How to Test: Run the following command to generate a map without the text overlays:

uv run python3 create_map_poster.py -c "Bengaluru" -C "India" --no-text

Verify that the output poster does not contain the city name, country name, coordinates, divider line, or bottom-right attribution, but correctly outputs the map and border layout. Alternatively, you can run the test/all_variations.sh script to verify it fits nicely alongside existing tests.

This is the result example for Tokyo, Japan