ci: remove post-merge ci.yml workflow

It duplicated the developer-machine quality gate (tsc + npm build + compileall),
ran post-merge on main (not a pre-merge gate), and would put the heavy frontend
build on the small prod VPS on every push — the very load deploy.yml deliberately
keeps on the dev box. The local pre-ship checks are the CI in this setup.

.forgejo/workflows/ci.yml

@@ -1,35 +0,0 @@
-name: CI
-# Lightweight validation on every push to main: type-check + build the frontend and
-# byte-compile the backend. The image build and rollout happen on the deploy host
-# (see deploy/README.md); this just catches breakage early.
-on:
-  push:
-    branches: [main]
-  workflow_dispatch:
-
-jobs:
-  frontend:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-node@v4
-        with:
-          node-version: "20"
-      - run: npm ci
-        working-directory: frontend
-      - run: npx tsc --noEmit
-        working-directory: frontend
-      - run: npm run build
-        working-directory: frontend
-
-  backend:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-python@v5
-        with:
-          python-version: "3.12"
-      - run: pip install -r requirements.txt
-        working-directory: backend
-      - run: python -m compileall -q app
-        working-directory: backend