Guard pre-1.3 report shims with function_exists to avoid redeclare fatal

[TheWitness]

Problem

includes/functions.php loads the pre-1.3 report compatibility shims with a
version-string gate:

if (version_compare(CACTI_VERSION, '1.3', '<')) {
    require_once(__DIR__ . '/functions-pre13.php');
}

functions-pre13.php unconditionally defines reports_run(),
reports_queue(), and reports_log_and_notify(). Cacti core defines all three
natively in lib/reports.php on 1.3. Current develop builds still report a
version that compares < 1.3, so this block loads the shims even though the
native functions already exist, producing a Cannot redeclare reports_run()
fatal on flowview's report pages and the report poller.

This is the same unreliable CACTI_VERSION gating that was just fixed in
plugin_monitor (#270); here it surfaces as a hard fatal rather than a UI hang.

Fix

Gate on the actual presence of the functions rather than the version string.
Core adds all three together, so checking the representative reports_run() is
sufficient:

if (!function_exists('reports_run')) {
    require_once(__DIR__ . '/functions-pre13.php');
}

• True legacy Cacti (< 1.3, functions absent): shims load as before.
• Cacti 1.3 and any develop build that reports < 1.3 while already defining
  the functions natively: shims are skipped, no redeclare.

functions-pre13.php is loaded only from this one site (verified), so no other
include path can trip the redeclare.

Testing

• php -l includes/functions.php — no syntax errors.

[Copilot]

🟡 Changes recommended

The develop-only redeclaration scenario lacks targeted regression coverage.

1 open finding

• Add isolated test for native report function redeclaration regression · New

What changed in this PR

Updates report compatibility loading to avoid function redeclaration failures on Cacti develop builds.

Changes:

• Replaces version-based shim loading with a function_exists() guard.
• Documents the fix in the changelog.

File	Description
includes/​functions.php	Guards legacy report shims using runtime function availability.
CHANGELOG.md	Records the compatibility fix.

🧠 Review effort: Balanced

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