feat(board-channels): skip Slack createChannel in dev/test mode

Mirrors the dev-mode short-circuit in invite.post.js. Without
SLACK_BOT_TOKEN, board-channel create returned 500 'Slack integration
not configured', breaking e2e in CI. With ALLOW_DEV_TEST_ENDPOINTS=true,
generate a stub channel ID and proceed; everything DB-side still runs.

server/api/admin/board-channels.post.js

@@ -24,22 +24,27 @@ export default defineEventHandler(async (event) => {
   let channelName = body.name
 
   if (!slackChannelId) {
-    const slack = getSlackAdminService()
-    if (!slack) {
-      throw createError({
-        statusCode: 500,
-        statusMessage: 'Slack integration not configured',
-      })
-    }
-    try {
-      const created = await slack.createChannel(body.name)
-      slackChannelId = created.id
-      channelName = created.name
-    } catch (err) {
-      throw createError({
-        statusCode: 502,
-        statusMessage: `Failed to create Slack channel: ${err.data?.error || err.message}`,
-      })
+    if (process.env.ALLOW_DEV_TEST_ENDPOINTS === 'true') {
+      slackChannelId = `dev-stub-${Date.now()}`
+      console.log('[slack] DEV MODE — skipping createChannel', { name: body.name, slackChannelId })
+    } else {
+      const slack = getSlackAdminService()
+      if (!slack) {
+        throw createError({
+          statusCode: 500,
+          statusMessage: 'Slack integration not configured',
+        })
+      }
+      try {
+        const created = await slack.createChannel(body.name)
+        slackChannelId = created.id
+        channelName = created.name
+      } catch (err) {
+        throw createError({
+          statusCode: 502,
+          statusMessage: `Failed to create Slack channel: ${err.data?.error || err.message}`,
+        })
+      }
     }
   }