feat(projects): list + create API and creatable ProjectAutocomplete (T4)

- GET /api/projects returns the shared global list; POST /api/projects
  creates a project, deduped case-insensitively (F3).
- Repository find-or-create trims and matches on lower(name); a unique index
  on lower(name) enforces the same rule at the DB (replacing the case-
  sensitive column unique constraint) — migration 0001.
- ProjectAutocomplete: creatable autocomplete that lists projects, offers to
  create an unknown name inline, and selects it without reload.
- Integration test (dedupe/list against Postgres) + component test.

server/api/projects.post.ts

@@ -0,0 +1,12 @@
+import { getDb } from '../db/client'
+import { createProject } from '../db/repositories/projects'
+
+// Create a project (case-insensitively deduped) and return it (F3).
+export default defineEventHandler(async (event) => {
+  const body = await readBody<{ name?: unknown }>(event)
+  const name = typeof body?.name === 'string' ? body.name.trim() : ''
+  if (!name) {
+    throw createError({ statusCode: 400, statusMessage: 'Project name is required' })
+  }
+  return createProject(getDb(), name)
+})