Fix GE Cloud Direct EVC API 422 errors after BST clock change

[Copilot]

After clocks move to BST (UTC+1), now_utc_exact returns local time but timestamps were formatted with a Z suffix (UTC), sending times 1 hour ahead to the GivEnergy EVC API — causing 422 errors. The EVC device always operates on GMT regardless of local clock.

Changes

• gecloud.py: Convert now_utc_exact to UTC via .astimezone(timezone.utc) before formatting timestamps in async_get_evc_device_data and async_get_evc_sessions

# Before — formats BST time but appends Z (meaning UTC)
now = self.now_utc_exact

# After — always sends correct UTC value
now = self.now_utc_exact.astimezone(timezone.utc)

• tests/test_ge_cloud.py: Updated mock _now_utc_exact to be timezone-aware; added BST test scenarios verifying the API receives UTC times when now_utc_exact is in BST (UTC+1)

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[Copilot]

Pull request overview

Fixes GivEnergy GE Cloud Direct EVC API request timestamps after the UK clock change to BST (UTC+1) by ensuring timestamps formatted with a trailing Z are actually UTC (preventing 422 “unprocessable entity” errors from the EVC API, which expects GMT/UTC times).

Changes:

• Convert now_utc_exact to UTC via .astimezone(timezone.utc) before generating start_time/end_time for EVC sessions and device data requests.
• Update GE Cloud tests to use timezone-aware now_utc_exact mocks and add BST-specific scenarios asserting the API receives UTC Z timestamps.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
apps/predbat/gecloud.py	Ensures EVC start_time/end_time query parameters are derived from a UTC datetime when formatting with Z.
apps/predbat/tests/test_ge_cloud.py	Makes mocked times timezone-aware and adds BST coverage to prevent regressions around DST transitions.

[bpinto]

I believe there is a pattern of using now_local. IMO these variables that have a suffix of _utc would be better if they were renamed to _local suffix.

It's hard to understand this line since one would expect the self.now_utc_exact to already be in UTC timezone.

[springfall2008]

Rather confusingly the UTC refers to TZ aware formats and not UTC time