Add build optimization design doc

docs/plans/2026-02-21-build-optimization-design.md

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+# Build Optimization Design
+
+## Goal
+
+Minimize Docker build times and production image sizes for both the backend (Python/FastAPI) and frontend (React/Vite) builds.
+
+## Changes
+
+### 1. Dependency Cleanup
+
+#### Backend: Remove from pyproject.toml
+
+| Package | Reason | Replacement |
+|---------|--------|-------------|
+| `watchdog` | Zero production imports | None |
+| `tqdm` | Progress bars in 4 files | `logging.info()` |
+| `pandas` | CSV export only (1 file) | `csv.DictWriter` |
+| `apprise` | Notifications (1 file) | Remove |
+| `opencv-python` | Includes GUI libs (~40MB) | `opencv-python-headless` |
+
+#### Backend: Fix missing prod dep
+
+- Add `httpx` to production dependencies (imported in `api/auth.py` but currently dev-only).
+
+#### Frontend: Remove from package.json
+
+| Package | Reason |
+|---------|--------|
+| `@tabler/icons-react` | Zero imports, replaced by `lucide-react` |
+| `crossfilter2` | Zero imports |
+| `date-fns` | Zero imports, replaced by `chrono-node` |
+
+#### Frontend: Move to devDependencies
+
+- `@types/crossfilter`, `@types/d3`, `@types/mapbox-gl`, `@types/turf`
+
+### 2. Backend Dockerfile
+
+- Add `# syntax=docker/dockerfile:1` for BuildKit support.
+- Replace `pip` with `uv` (10-25x faster). Copy binary from `ghcr.io/astral-sh/uv:latest`.
+- Add BuildKit cache mounts for `/var/cache/apt`, `/var/lib/apt/lists`, `/root/.cache/uv`.
+- Remove `--no-cache-dir` from pip install (cache mount handles this).
+- Remove `libgl1` from runtime-base (`opencv-python-headless` doesn't need it).
+- Add non-root `appuser` in the final stage.
+- Add `HEALTHCHECK` using curl to `/health`.
+
+### 3. Frontend Dockerfile
+
+- Add `# syntax=docker/dockerfile:1` for BuildKit support.
+- Add npm cache mount (`/root/.npm`) for `npm ci`.
+- Add non-root nginx user.
+- Add `HEALTHCHECK`.
+
+### 4. CI Pipeline (Drone)
+
+- Enable BuildKit in the API pipeline (`DOCKER_BUILDKIT=1` in `plugins/docker` settings).
+- Frontend pipeline (Kaniko) already has good caching; no changes needed.
+
+### 5. Source Code Changes
+
+#### tqdm removal
+
+Replace `tqdm` progress bars with `logging.info` in:
+- `services/image_fetcher.py`
+- `services/floorplan_detector.py`
+- `services/route_calculator.py`
+- `repositories/listing_repository.py`
+
+#### pandas removal
+
+Rewrite CSV export in the file that imports pandas to use `csv.DictWriter`.
+
+#### apprise removal
+
+Remove `notifications.py` or its apprise-dependent code.
+
+#### requirements.txt regeneration
+
+After updating `pyproject.toml`, regenerate with `poetry export --without-hashes -f requirements.txt -o requirements.txt` (or with hashes if preferred).
+
+## Expected Impact
+
+- **Image size**: ~50-80MB reduction (headless OpenCV, removed deps).
+- **Local rebuild speed**: 2-5x faster on cache hits (BuildKit mounts + uv).
+- **CI rebuild speed**: Moderate improvement from BuildKit layer caching; cache mounts are ephemeral in CI but layer caching already works.
+- **Security**: Non-root user in both production images.