feat: board post + channel API routes

Implements Phase 2a of board classifieds redesign:

- GET/POST /api/board/posts (list with tag/author filters, create)
- PATCH/DELETE /api/board/posts/:id (author-only)
- GET /api/board/channels (member)
- POST /api/admin/board-channels (admin)
- PATCH/DELETE /api/admin/board-channels/:id (admin)

Adds board_post_created activity type.

server/api/board/posts/[id].delete.js

@@ -0,0 +1,20 @@
+import BoardPost from '../../../models/boardPost.js'
+import { requireAuth } from '../../../utils/auth.js'
+
+export default defineEventHandler(async (event) => {
+  const member = await requireAuth(event)
+  const id = getRouterParam(event, 'id')
+
+  const post = await BoardPost.findById(id)
+  if (!post) {
+    throw createError({ statusCode: 404, statusMessage: 'Post not found' })
+  }
+
+  if (post.author.toString() !== member._id.toString()) {
+    throw createError({ statusCode: 403, statusMessage: 'Not authorized to delete this post' })
+  }
+
+  await post.deleteOne()
+
+  return { success: true }
+})

server/api/board/posts/[id].patch.js

@@ -0,0 +1,52 @@
+import BoardPost from '../../../models/boardPost.js'
+import { requireAuth } from '../../../utils/auth.js'
+import { validateBody } from '../../../utils/validateBody.js'
+import { boardPostUpdateSchema } from '../../../utils/schemas.js'
+
+export default defineEventHandler(async (event) => {
+  const member = await requireAuth(event)
+  const id = getRouterParam(event, 'id')
+
+  const body = await validateBody(event, boardPostUpdateSchema)
+
+  const post = await BoardPost.findById(id)
+  if (!post) {
+    throw createError({ statusCode: 404, statusMessage: 'Post not found' })
+  }
+
+  if (post.author.toString() !== member._id.toString()) {
+    throw createError({ statusCode: 403, statusMessage: 'Not authorized to edit this post' })
+  }
+
+  if (body.title !== undefined) post.title = body.title
+  if (body.seeking !== undefined) post.seeking = body.seeking
+  if (body.offering !== undefined) post.offering = body.offering
+  if (body.note !== undefined) post.note = body.note
+  if (body.tags !== undefined) post.tags = body.tags
+
+  const seeking = (post.seeking || '').trim()
+  const offering = (post.offering || '').trim()
+  if (!seeking && !offering) {
+    throw createError({
+      statusCode: 400,
+      statusMessage: 'At least one of seeking or offering must be provided'
+    })
+  }
+
+  try {
+    await post.save()
+  } catch (err) {
+    if (err.name === 'ValidationError') {
+      throw createError({
+        statusCode: 400,
+        statusMessage: 'Validation failed',
+        data: err.errors
+      })
+    }
+    throw err
+  }
+
+  await post.populate('author', 'name avatar circle board.slackHandle')
+
+  return { post: post.toObject() }
+})