Add getArgusImagery function for FRF tower orthophoto retrieval

[SBFRF]

Summary

• Adds getArgusImagery() function to retrieve Argus orthophoto imagery from the FRF coastal imaging server (coastalimaging.erdc.dren.mil)
• Adds threadGetArgusImagery() for non-blocking background downloads
• Supports image types: timex, var, snap, brightest, darkest
• Images available every 30 minutes; function rounds input time to nearest interval

Test plan

• Unit tests added for URL construction, time rounding, error handling
• Unit tests for threaded version verify non-blocking behavior
• All tests pass (pytest tests/test_getDataFRF.py -v -m "not slow")
• Manual test with network access to verify actual image retrieval

Closes #18

🤖 Generated with Claude Code

[SBFRF]

Additional changes in this update

This PR now also includes:

New utility function

• get_geotiff_extent(): Parses GeoTIFF ModelTiepointTag and ModelPixelScaleTag to extract matplotlib extent (uses tifffile, no GDAL needed)

New example script

• examples/test_wave_and_imagery.py: Demonstrates wave data + imagery overlay
  • Fetches wave data from all FRF gauges (last 30 days)
  • Retrieves satellite imagery via getSatelliteImagery()
  • Retrieves Argus orthophoto via getArgusImagery()
  • Converts Argus State Plane coords to lat/lon using geoprocess.FRFcoord()
  • Creates 2-panel figure: wave height time series (top) + gauge locations over imagery with Argus overlay at 50% opacity (bottom)

Test

python examples/test_wave_and_imagery.py

[SBFRF]

lgtm