ci: drop backend pytest stage (too slow on hosted runner)

The editable install of core+server+dev pulls the full scientific Python
stack (SQLAlchemy, aiohttp, pytest, httpx, slowapi, uvicorn[standard],
apscheduler and their transitives) on every CI run. Even with pip cache
the restore + install takes minutes per job — not worth it for a suite
that still runs locally via ``pytest packages/server/tests``.

Kept the frontend svelte-check + build and the non-push Docker image
build. Release workflow no longer has a test gate either (same reason).
Bring the test stage back once we have a prebuilt CI image with deps.

.gitea/workflows/build.yml

@@ -8,32 +8,6 @@ on:
   workflow_dispatch:
 
 jobs:
-  test-backend:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v4
-
-      - name: Set up Python
-        uses: actions/setup-python@v5
-        with:
-          python-version: "3.12"
-          cache: "pip"
-          cache-dependency-path: |
-            packages/core/pyproject.toml
-            packages/server/pyproject.toml
-
-      - name: Install core + server + dev deps (in venv)
-        run: |
-          python -m venv .venv
-          . .venv/bin/activate
-          python -m pip install -e ./packages/core -e "./packages/server[dev]"
-
-      - name: Run pytest (server)
-        run: |
-          . .venv/bin/activate
-          cd packages/server
-          pytest -q --maxfail=1
-
   test-frontend:
     runs-on: ubuntu-latest
     steps:
@@ -62,7 +36,7 @@ jobs:
           npm run build
 
   build-image:
-    needs: [test-backend, test-frontend]
+    needs: [test-frontend]
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v4

.gitea/workflows/release.yml

@@ -10,26 +10,7 @@ env:
   IMAGE_NAME: alexei.dolgolyov/notify-bridge
 
 jobs:
-  test:
-    runs-on: ubuntu-latest
-    steps:
-      - uses: actions/checkout@v4
-      - uses: actions/setup-python@v5
-        with:
-          python-version: "3.12"
-          cache: "pip"
-          cache-dependency-path: |
-            packages/core/pyproject.toml
-            packages/server/pyproject.toml
-      - name: Install + test (in venv, isolated from hosted tool cache)
-        run: |
-          python -m venv .venv
-          . .venv/bin/activate
-          python -m pip install -e ./packages/core -e "./packages/server[dev]"
-          cd packages/server && pytest -q --maxfail=1
-
   release:
-    needs: test
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repo