EasyIQ (0001): surface API errors and schema mismatches at WARNING level

[spraot]

Summary

The legacy EasyIQ block (widget 0001) wraps the Events iteration in a bare:

try:
    for i in ugeplaner.json()["Events"]:
        ...
except KeyError:
    _LOGGER.debug("None")

Any non-Events response — including the EasyIQ error envelope {"ErrorCode": "1", "ErrorDescription": "..."}, which the API now returns aggressively for schools that have migrated to SkolePortal but still have widget 0001 listed — falls into the except and is logged at DEBUG level as the literal string "None". Downstream, the sensor attribute renders as just <h2> Uge NN</h2> for every child with no log line at default verbosity indicating why.

This PR makes two small additions, no behaviour change for happy paths:

1. After the existing DEBUG dump of the response, detect the EasyIQ error envelope shape and log it as a WARNING naming widget id, child, institution header, week, ErrorCode and ErrorDescription.
2. Replace except KeyError: _LOGGER.debug("None") with a WARNING that names the missing key and the response keys it did see — so the next EasyIQ schema change isn't silent either.

Genuine empty weeks for a child still produce no warnings (the date-format check still DEBUG-logs to a "None"-style line, just with more context).

Why

Filed as a follow-up to the drive-by suggestion on #352. The silent-failure mode cost a couple of hours of diagnostic time before enabling debug logging revealed the actual ErrorCode/ErrorDescription payload. Surfacing it at default verbosity should save the next person the same archaeology.

Test plan

• Module syntax-checks clean (python3 -c 'import ast; ast.parse(...)').
• Verified locally on HAOS against the equivalent surfacing path (applied as part of an earlier patch); the WARNING fires once per child per week when EasyIQ returns the license error, and the sensor body is unchanged for genuine empty weeks.
• @MartinSaaby offered on Add EasyIQ SkolePortal support (widget 0128) #352 to verify the WARNING fires correctly on a SkolePortal-only school whose widget list still contains 0001.