Phase 7: MIT license, portfolio README, Docker, cross-platform start

- LICENSE: MIT
- README: rewritten as portfolio-grade docs (features with code pointers,
  architecture, Docker/Windows/macOS quick starts, BYO-model table)
- Dockerfile (3-stage: SPA build, pip wheels, slim runtime) + compose with
  a /data volume; .dockerignore keeps secrets and local data out
- database.py: AIDND_DB_PATH env override so deployments can relocate the
  SQLite file; documented in backend/.env.example
- start.sh: macOS/Linux dev script with first-run setup

Verified locally: production SPA build served by the backend (deep links
OK), DB created at the override path. Docker image itself untested here
(Docker not installed); flagged in plan/07.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KFsGHju9szibJJa2YJcdbg

Dockerfile

@@ -0,0 +1,35 @@
+# Stage 1 — build the React SPA
+FROM node:22-alpine AS frontend-build
+WORKDIR /build
+COPY frontend/package.json frontend/package-lock.json ./
+RUN npm ci
+COPY frontend/ ./
+RUN npm run build
+
+# Stage 2 — build Python wheels (quickjs compiles from source if no wheel
+# matches, so keep the toolchain out of the final image)
+FROM python:3.12-slim AS python-build
+RUN apt-get update && apt-get install -y --no-install-recommends gcc make \
+    && rm -rf /var/lib/apt/lists/*
+COPY backend/requirements.txt /tmp/requirements.txt
+RUN pip wheel --no-cache-dir -r /tmp/requirements.txt -w /wheels
+
+# Stage 3 — runtime
+FROM python:3.12-slim
+WORKDIR /app
+
+COPY --from=python-build /wheels /wheels
+RUN pip install --no-cache-dir /wheels/* && rm -rf /wheels
+
+# Layout mirrors the repo: main.py finds the SPA at ../../frontend/dist
+# relative to backend/app/main.py.
+COPY backend/app /app/backend/app
+COPY --from=frontend-build /build/dist /app/frontend/dist
+
+# Database lives on a volume; parent dir is created by the app if missing.
+ENV AIDND_DB_PATH=/data/data.db
+VOLUME /data
+
+EXPOSE 8000
+WORKDIR /app/backend
+CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "8000"]