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>

goodnews/moods.py

@@ -0,0 +1,62 @@
+"""Mood modes — the humane front door over the topic/flavor taxonomy.
+
+A reader thinks "I want wonder," not "animals/discovery". Each mood resolves to
+a filter preset (include_topics / include_flavors / a cortisol ceiling) that the
+feed already understands via FilterPrefs. Topic/flavor remain available as the
+secondary "browse more precisely" controls; moods don't replace them.
+
+Single source of truth so the website and any future companion app agree.
+"""
+
+from __future__ import annotations
+
+# "today" is special: it has no filter — it's the daily brief view.
+MOODS: list[dict] = [
+    {
+        "key": "today",
+        "label": "Today",
+        "description": "The day's five good things.",
+        "filter": {},
+    },
+    {
+        "key": "wonder",
+        "label": "Wonder",
+        "description": "Awe and discovery.",
+        "filter": {"include_topics": ["science", "animals", "culture"], "include_flavors": ["discovery"]},
+    },
+    {
+        "key": "people-helping",
+        "label": "People Helping",
+        "description": "Community, kindness, and repair.",
+        "filter": {"include_topics": ["community"], "include_flavors": ["solution", "feelgood"]},
+    },
+    {
+        "key": "solutions",
+        "label": "Solutions",
+        "description": "Problems being solved.",
+        "filter": {
+            "include_topics": ["environment", "community", "health"],
+            "include_flavors": ["solution", "breakthrough"],
+        },
+    },
+    {
+        "key": "light",
+        "label": "Light Only",
+        "description": "Just the gentle stuff.",
+        "filter": {"include_flavors": ["feelgood", "discovery"], "max_cortisol": 2},
+    },
+    {
+        "key": "grounded",
+        "label": "Grounded",
+        "description": "Useful, calm perspective.",
+        "filter": {"include_flavors": ["perspective", "solution"]},
+    },
+]
+
+_BY_KEY = {m["key"]: m for m in MOODS}
+
+
+def mood_filter(key: str) -> dict:
+    """Return the filter preset for a mood key (empty dict if unknown/today)."""
+    mood = _BY_KEY.get(key)
+    return dict(mood["filter"]) if mood else {}