Add CI workflow and warm-boot the slow lazy bits

GitHub Actions runs pytest on push/PR via uv. App lifespan now loads
the g2p model and builds the near-rhyme index at startup so the first
keystroke and first lookup are never slow.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.github/workflows/ci.yml

@@ -0,0 +1,17 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: astral-sh/setup-uv@v5
+        with:
+          enable-cache: true
+      - run: uv sync --frozen
+      - run: uv run pytest