Add AusTemp SST dataset configuration and refactor regex filtering

[Copilot]

Adds support for the AusTemp 8-day Sea Surface Temperature dataset with cloud-optimized Zarr format, including schema definitions for SST variables (sst, sst_mosaic, sst_mosaic_age, sst_anom, sst_anom_mosaic).

Changes

• New dataset configuration: satellite_austemp_sst_8day.json with complete schema and AWS OpenData Registry metadata
• Regex filter refactoring: Simplified file filtering in generic_cloud_optimised_creation.py from loop-based to single-pattern approach, leveraging existing field validator that converts filter lists to strings
• Filter pattern updates: Updated regex patterns in austemp and himawari8 configs (removed $ anchor for consistency with other satellite configs)
• Worker optimization: Reduced himawari8 nthreads from 4 to 1 for better memory management
• Documentation: Added/updated Jupyter notebooks for dataset access examples

Example

Before (looped over filter list):

for pattern in path_cfg.filter or []:
    regex = re.compile(pattern)
    matching_files = [f for f in matching_files if regex.search(f)]

After (single pattern, validator ensures string type):

pattern: str = path_cfg.filter or ".*"
regex = re.compile(pattern)
matching_files = [f for f in matching_files if regex.search(f)]

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