feat(webhook): skip deployment on [skip ci]/[skip cd] commit markers

Add DetectsSkipDeployCommits trait with two strategies: shouldSkipDeploy
(all commits must contain the marker) for push events, and
shouldSkipDeployAny (any single marker triggers skip) for PR/MR titles
and latest-commit signals.

Apply trait to Bitbucket, Gitea, GitHub, GitLab webhook controllers and
ProcessGithubPullRequestWebhook job. PRs pass pullRequestTitle through
to the job constructor for evaluation.

app/Http/Controllers/Webhook/Concerns/DetectsSkipDeployCommits.php

@@ -0,0 +1,55 @@
+<?php
+
+namespace App\Http\Controllers\Webhook\Concerns;
+
+trait DetectsSkipDeployCommits
+{
+    /**
+     * Returns true if there is at least one non-empty message and every message
+     * contains [skip cd] or [skip ci] (case-insensitive).
+     *
+     * Accepts commit messages from a push payload. Null/empty entries are
+     * filtered before evaluation.
+     *
+     * @param  array<int, string|null>  $messages
+     */
+    public static function shouldSkipDeploy(array $messages): bool
+    {
+        $messages = array_values(array_filter($messages, fn ($m) => filled($m)));
+
+        if (empty($messages)) {
+            return false;
+        }
+
+        foreach ($messages as $message) {
+            $lower = strtolower((string) $message);
+            if (! str_contains($lower, '[skip cd]') && ! str_contains($lower, '[skip ci]')) {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+    /**
+     * Returns true if at least one non-empty message contains [skip cd] or
+     * [skip ci]. Used for PR/MR title + latest-commit signals where any one
+     * marker should trigger the skip.
+     *
+     * @param  array<int, string|null>  $messages
+     */
+    public static function shouldSkipDeployAny(array $messages): bool
+    {
+        foreach ($messages as $message) {
+            if (! filled($message)) {
+                continue;
+            }
+            $lower = strtolower((string) $message);
+            if (str_contains($lower, '[skip cd]') || str_contains($lower, '[skip ci]')) {
+                return true;
+            }
+        }
+
+        return false;
+    }
+}