chore(v5): archive V5 implementation and remove runtime integration

Move V5 source, migrations, UI, scripts, and tests into documentation, then remove V5 routes, models, jobs, configuration, dependencies, and application hooks.

app/Exceptions/V5/UnsupportedCooldVerb.php

@@ -1,18 +0,0 @@
-<?php
-
-namespace App\Exceptions\V5;
-
-use RuntimeException;
-
-/**
- * The per-node coold agent does not implement the dispatched verb. Flux
- * rejects these before they reach the node, so callers can degrade
- * gracefully instead of treating the miss as an operational failure.
- */
-class UnsupportedCooldVerb extends RuntimeException
-{
-    public function __construct(public readonly string $verb, string $message = '')
-    {
-        parent::__construct($message !== '' ? $message : "The node's coold agent does not support the {$verb} verb.");
-    }
-}