fix: handle list response in get_solar_intensity to prevent bulk-update crash

[Deyi-dev]

Problem

get_solar_intensity() assumes get_device_solar_data() returns a dict:

si_all = garmin_obj.get_device_solar_data(GARMIN_DEVICEID, date_str) or {}
if len(si_all.get('solarDailyDataDTOs', [])) > 0:

On some dates Garmin returns a list instead. The or {} guard only covers None/empty (falsy) values — a non-empty list is truthy, so it passes straight through to si_all.get(...) and crashes the whole run:

File ".../garmin_fetch.py", line 1544, in get_solar_intensity
    if len(si_all.get('solarDailyDataDTOs', [])) > 0:
AttributeError: 'list' object has no attribute 'get'

This is fatal during a bulk backfill: one bad date aborts the entire date range. I hit it on 2026-07-08 while backfilling a solar-capable device (Fenix 7 Pro Solar) with solar_intensity in FETCH_SELECTION.

Fix

Normalize the response to the DTO list before indexing, handling both the dict and list shapes (and guarding the element access):

if isinstance(si_all, dict):
    solar_dtos = si_all.get('solarDailyDataDTOs', [])
elif isinstance(si_all, list):
    solar_dtos = si_all
else:
    solar_dtos = []
if len(solar_dtos) > 0 and isinstance(solar_dtos[0], dict):
    si_list = solar_dtos[0].get('solarInputReadings', [])

The dict path is unchanged; the list path no longer crashes; anything unexpected degrades to "no solar data for this date" instead of aborting the run. Verified by re-running the same 30-day backfill end-to-end with zero errors.