feat(ci): add smoke tests workflow + Lighthouse audit script

- .forgejo/workflows/smoke-tests.yml: checks all Go services + web apps
  every 6h, fails if any health check fails
- scripts/lighthouse-audit.sh: runs Lighthouse on all 14 web apps

Initial Lighthouse results:
  mana.how:      Perf:80  A11y:96  BP:100 SEO:92
  todo.mana.how: Perf:69  A11y:96  BP:100 SEO:100
  chat.mana.how: Perf:83  A11y:100 BP:96  SEO:92

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

scripts/lighthouse-audit.sh

@@ -0,0 +1,60 @@
+#!/bin/bash
+# Lighthouse Performance Audit for all ManaCore web apps
+# Requires: npx (for lighthouse CLI)
+# Usage: ./scripts/lighthouse-audit.sh [--json]
+
+set -e
+
+JSON_MODE=false
+[ "$1" = "--json" ] && JSON_MODE=true
+
+APPS=(
+  "mana.how"
+  "chat.mana.how"
+  "todo.mana.how"
+  "calendar.mana.how"
+  "clock.mana.how"
+  "contacts.mana.how"
+  "storage.mana.how"
+  "presi.mana.how"
+  "nutriphi.mana.how"
+  "zitare.mana.how"
+  "photos.mana.how"
+  "skilltree.mana.how"
+  "picture.mana.how"
+  "mukke.mana.how"
+)
+
+RESULTS_DIR="lighthouse-results"
+mkdir -p "$RESULTS_DIR"
+
+echo "=== ManaCore Lighthouse Audit ==="
+echo "Date: $(date -u +%Y-%m-%dT%H:%M:%SZ)"
+echo ""
+
+for app in "${APPS[@]}"; do
+  echo -n "$app... "
+  URL="https://$app"
+
+  OUTPUT="$RESULTS_DIR/$(echo $app | tr '.' '-').json"
+
+  npx lighthouse "$URL" \
+    --output=json \
+    --output-path="$OUTPUT" \
+    --chrome-flags="--headless --no-sandbox" \
+    --only-categories=performance,accessibility,best-practices,seo \
+    --quiet 2>/dev/null
+
+  if [ -f "$OUTPUT" ]; then
+    PERF=$(cat "$OUTPUT" | python3 -c "import sys,json; print(int(json.load(sys.stdin)['categories']['performance']['score']*100))" 2>/dev/null || echo "?")
+    A11Y=$(cat "$OUTPUT" | python3 -c "import sys,json; print(int(json.load(sys.stdin)['categories']['accessibility']['score']*100))" 2>/dev/null || echo "?")
+    BP=$(cat "$OUTPUT" | python3 -c "import sys,json; print(int(json.load(sys.stdin)['categories']['best-practices']['score']*100))" 2>/dev/null || echo "?")
+    SEO=$(cat "$OUTPUT" | python3 -c "import sys,json; print(int(json.load(sys.stdin)['categories']['seo']['score']*100))" 2>/dev/null || echo "?")
+    echo "Perf:$PERF A11y:$A11Y BP:$BP SEO:$SEO"
+  else
+    echo "FAILED"
+  fi
+done
+
+echo ""
+echo "Results saved to $RESULTS_DIR/"