refactor: extract the duplicated timespan lookup in cycle.php

[somethingwithproof]

cycle_graphs() and cycle() built the graph timespan with the same three lines. This moves them into cycle_get_timespan() and calls it from both.

Also drops a stray space before a comma at the second call site.

Rebuilt on current develop. The earlier version of this branch predated #27, which had already converted the array syntax, so most of it was redundant and it no longer rebased cleanly.

No behaviour change.

[Copilot]

Pull request overview

This PR modernizes the Cycle plugin’s PHP files by enabling strict typing and updating some legacy syntax to PHP 7.4-era constructs.

Changes:

• Added declare(strict_types=1); across plugin PHP entrypoints.
• Converted some array(...) usages to short array syntax ([...]) and updated prepared-statement parameter arrays accordingly.
• Introduced two .omc/sessions/*.json files (appear to be local tooling artifacts).

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
setup.php	Adds strict typing and updates a couple of arrays to short syntax.
functions.php	Adds strict typing and partially modernizes arrays/params in several functions.
cycle.php	Adds strict typing and updates a few array() initializations / prepared params.
index.php	Adds strict typing to the plugin redirect entrypoint.
images/index.php	Adds strict typing to the redirect stub.
locales/index.php	Adds strict typing to the redirect stub.
locales/LC_MESSAGES/index.php	Adds strict typing to the redirect stub.
.omc/sessions/859688d5-ece7-4d1e-ab13-c82d820e7440.json	New session JSON file (likely unintended).
.omc/sessions/42a5a3ed-3430-434f-addf-dc7423bda6d8.json	New session JSON file (likely unintended).

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[somethingwithproof]

Converted to draft to serialize the stack in this repo. Blocked by #27; will un-draft after that merges to avoid cross-PR merge conflicts.