Build the SvelteKit frontend: calm home with mood modes

- New frontend/ SvelteKit static SPA (Svelte 5), served by FastAPI from
  frontend/build (falls back to the legacy page if unbuilt).
- Calm design system: cream/sage palette, serif headlines, generous space,
  no urgency colors, gentle motion (respects prefers-reduced-motion).
- Home screen: mood-mode nav (Today/Wonder/People Helping/Solutions/Light
  Only/Grounded), the daily brief as a hero + remaining four, browsable mood
  lanes, an explicit calm end-state, inline Not today / Less like this / Hide
  affordances, and device-local Calm Filters mirroring goodnews/filters.py.
- Backend: moods.py + GET /api/moods (single source of truth for the modes);
  FilterPrefs gains max_cortisol/max_ragebait ceilings (for Light Only).
- Push categorical filters (include/mute topics+flavors, ceilings) into SQL in
  queries.feed so low-ranked-but-matching items (e.g. discovery for Wonder)
  are not truncated by ranking; only avoid-terms stay a Python pass.
- PWA manifest + icon (installable; offline deferred per plan).
- Multi-stage Dockerfile builds the site then serves it from the API.
- Tests: queries.feed categorical filters (63 total). README updated.

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

Dockerfile

@@ -1,19 +1,30 @@
-# goodNews web/API image.
+# goodNews web/API image (multi-stage: build the SvelteKit site, then serve it
+# from the FastAPI app).
 #
-# The SQLite database is NOT baked into the image — mount it at /data so the API
-# and the ingestion CLI (run separately, e.g. via cron on the host) share one
+# The SQLite database is NOT baked in — mount it at /data so the API and the
+# ingestion CLI (run separately, e.g. via cron/systemd on the host) share one
 # file. Build:  docker build -t goodnews .
 # Run:    docker run -p 8000:8000 -v /srv/goodnews/data:/data goodnews
-FROM python:3.13-slim
 
+# --- Stage 1: build the static frontend ---
+FROM node:22-slim AS web
+WORKDIR /web
+COPY frontend/package.json frontend/package-lock.json ./
+RUN npm ci
+COPY frontend/ ./
+RUN npm run build
+
+# --- Stage 2: the Python API, serving the built site ---
+FROM python:3.13-slim
 WORKDIR /app
 
-# Install dependencies first for better layer caching.
 COPY pyproject.toml README.md ./
 COPY goodnews ./goodnews
 RUN pip install --no-cache-dir ".[web]"
 
-# API reads the database from here; mount a host dir or named volume.
+# FastAPI serves this directory (goodnews/api.py: FRONTEND_DIR = ROOT/frontend/build).
+COPY --from=web /web/build ./frontend/build
+
 ENV GOODNEWS_DB=/data/goodnews.sqlite3
 VOLUME ["/data"]