Add Sentinel-1D support

[dbekaert]

Summary

Adds Sentinel-1D support across the pipeline: AUX_CAL downloads, DAAC metadata schema, and SLC validation.

Changes

AUX_CAL downloads (localize_aux_cal.py)

• S1A/S1B: continue using ASF CloudFront bundles as baseline
• All missions (S1A–D): supplement from ESA SAR-MPC API (https://sar-mpc.eu/api/v1/) to pick up newer files and S1C/S1D entries
• Handles pagination and skip-if-exists caching

SLC validation (localize_slc.py)

• Added S1D_MIN_DATE (2026-04-17) placeholder to reject uncalibrated S1D acquisitions, mirroring the existing S1C_MIN_DATE check
• Updated error messages to include S1D

Metadata (daac_ingest_schema.json)

• Added Sentinel-1D to platform enum

Tests (test_localize_slc.py)

• Added test for S1D minimum date validation
• Updated error match patterns

Upstream dependencies

• s1_orbits: Already supports S1D via S1[ABCD] regex — no changes needed
• ISCE2: Requires S1D track number offset (42) in Sentinel1.py — see isce2#28123 (pending merge)

Notes

• S1D_MIN_DATE is a placeholder — update once S1D calibration is officially confirmed by ESA
• S1D orbit offset (42) is based on the commissioning orbit and may change when S1D moves to its final orbit (expected summer 2026)

[dbekaert]

ASF/DAAC Ingest Coordination
@asjohnston-asf — heads up on a potential ingest concern.

This PR adds "Sentinel-1D" (and "Sentinel-1C") to the platform enum in the producer-side DAAC ingest schema (daac_ingest_schema.json). When S1D products are generated, the JSON metadata will include "platform": ["Sentinel-1D", ...].

Question: Does ASF's receiving-side ingest validation / CMR collection configuration already support Sentinel-1D as a valid platform value? If not, S1D products would pass our local schema validation but could fail on ingest.

Specifically wondering about:

Server-side schema validation of the platform field
CMR collection metadata for the GUNW product suite
Any downstream search/discovery services that filter by platform

[dbekaert]

@cmarshak Can you keep an eye on this? We should do a test when the dependencies are ready.