Phase 9a: Schulkalender — Bundesland-Auswahl + Monatsansicht mit Ferien

Backend (school-service):
  - cal_public_event (region, event_type, name_de, name_en, start/end,
    UNIQUE(region, event_type, name_de, start_date)) — global snapshot.
  - cal_school_config (user_id PRIMARY KEY, bundesland, school year dates).
  - cal_school_event — Schul-eigene Termine; CRUD folgt in 9b.
  - GET /calendar/holidays?region=&from=&to= — Range-Query against
    cal_public_event, ordered by start_date.
  - GET / PUT /calendar/config — upsert Bundesland per User.
  - SeedFromSnapshot reads internal/seed/calendar_holidays.json on every
    boot; idempotent via the unique constraint. Async goroutine so the
    HTTP server starts immediately even if the seed file is large.

Data source:
  - scripts/calendar-snapshot.sh ruft openholidaysapi.org fuer alle 16
    Bundeslaender x 3 Schuljahre und schreibt
    school-service/internal/seed/calendar_holidays.json (854 Events,
    Stand Schuljahre 2026-2028).
  - Dockerfile kopiert das seed/-Verzeichnis ins Image, damit die
    Container-Datenbank beim ersten Start gefuellt wird.

Frontend (studio-v2):
  - /schulkalender Page mit Gradient + Blobs wie /stundenplan und
    /korrektur — gleicher Visual-Style.
  - BundeslandWizard: zeigt alle 16 Laender als Dropdown, speichert
    bei Klick die Config und switcht zur Monatsansicht.
  - MonthView: 6-Wochen-Grid Mo-So, Feiertage rose-toned, Schulferien
    amber-toned, heutiges Datum mit Indigo-Ring. Prev/Next/Heute
    Navigation.
  - lib/schulkalender/api.ts re-uses the stundenplan JWT helper so
    auth-mode wechselt nicht.
  - Sidebar bekommt einen Schulkalender-Eintrag (Icon mit Datum-Dots,
    Pfad /schulkalender) in allen 26 Sprachen.

Tests:
  - Go: 3 neue Validator-Tests (Bundesland len=5, EventType oneof,
    Pflichtfelder). 77 Tests gesamt, alle gruen.
  - Playwright: e2e/schulkalender.spec.ts mit Wizard, Save-Flow,
    MonthView-Render, Heute-Button, Sidebar-Link. Hermetisch via
    mockCalendarApi.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/calendar-snapshot.sh

@@ -0,0 +1,86 @@
+#!/usr/bin/env bash
+# Snapshot Public Holidays + School Holidays for all 16 German Bundeslaender
+# from openholidaysapi.org. The result is committed to the repo and imported
+# at first DB boot by school-service. Re-run yearly (or whenever the next
+# school year's data needs to be added).
+#
+# Usage:  bash scripts/calendar-snapshot.sh [FIRST_YEAR] [LAST_YEAR]
+#         defaults: current year .. current year + 2
+#
+# Output: school-service/internal/seed/calendar_holidays.json
+#         shape: [{ region, event_type, name_de, name_en, start_date, end_date }, ...]
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+OUT="$ROOT/school-service/internal/seed/calendar_holidays.json"
+mkdir -p "$(dirname "$OUT")"
+
+START_YEAR="${1:-$(date +%Y)}"
+END_YEAR="${2:-$((START_YEAR + 2))}"
+API="https://openholidaysapi.org"
+
+# DE-XX codes for all 16 Bundeslaender (alphabetical).
+REGIONS=(
+  "DE-BW" "DE-BY" "DE-BE" "DE-BB" "DE-HB" "DE-HH" "DE-HE" "DE-MV"
+  "DE-NI" "DE-NW" "DE-RP" "DE-SL" "DE-SN" "DE-ST" "DE-SH" "DE-TH"
+)
+
+if ! command -v jq >/dev/null 2>&1; then
+  echo "jq is required (brew install jq)" >&2
+  exit 1
+fi
+
+TMP=$(mktemp)
+trap 'rm -f "$TMP"' EXIT
+echo '[]' > "$TMP"
+
+fetch() {
+  local endpoint="$1" region="$2" year="$3"
+  curl -sf -G "$API/$endpoint" \
+    --data-urlencode "countryIsoCode=DE" \
+    --data-urlencode "languageIsoCode=DE" \
+    --data-urlencode "validFrom=${year}-01-01" \
+    --data-urlencode "validTo=${year}-12-31" \
+    --data-urlencode "subdivisionCode=$region" \
+    || echo '[]'
+}
+
+# Map OpenHolidaysAPI shape → our DB schema. The API returns an array of:
+#   { id, startDate, endDate, type, name: [{ language, text }], ... }
+# We keep DE name as canonical, EN name if present, plus dates and a typed
+# event_type discriminator. PublicHolidays and SchoolHolidays come from two
+# separate endpoints.
+normalise_jq='
+  map({
+    region: $region,
+    event_type: $event_type,
+    name_de: ((.name // []) | map(select(.language == "DE")) | .[0].text // ""),
+    name_en: ((.name // []) | map(select(.language == "EN")) | .[0].text // null),
+    start_date: .startDate,
+    end_date: .endDate
+  }) | map(select(.name_de != ""))
+'
+
+for region in "${REGIONS[@]}"; do
+  for year in $(seq "$START_YEAR" "$END_YEAR"); do
+    echo "  $region $year — public" >&2
+    fetch "PublicHolidays" "$region" "$year" \
+      | jq --arg region "$region" --arg event_type "public_holiday" "$normalise_jq" \
+      | jq -s --slurpfile existing "$TMP" '$existing[0] + .[0]' > "$TMP.new"
+    mv "$TMP.new" "$TMP"
+
+    echo "  $region $year — school" >&2
+    fetch "SchoolHolidays" "$region" "$year" \
+      | jq --arg region "$region" --arg event_type "school_holiday" "$normalise_jq" \
+      | jq -s --slurpfile existing "$TMP" '$existing[0] + .[0]' > "$TMP.new"
+    mv "$TMP.new" "$TMP"
+  done
+done
+
+# Deduplicate (the API sometimes returns overlapping rows for events that
+# straddle a year boundary) and sort for a stable diff.
+jq 'unique_by({region, event_type, name_de, start_date}) | sort_by([.region, .start_date])' \
+   "$TMP" > "$OUT"
+
+echo
+echo "Wrote $(jq length "$OUT") events to $OUT"