fix(strommix): show sparkline without history backend

The strommix_history_de collection source URL 404s (Energy-Charts needs
start/end params), so the CMS history backend stays empty and todayHourly
was always null — making the Wind & Solar sparkline never appear.

Extend fetchEnergyChartsPublicPower to start at midnight (was: -2h) and
return the raw series alongside the snapshot values. Build todayHourly
from it when the history backend has no items. No extra API call.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/routes/api/strommix/+server.ts

@@ -46,13 +46,6 @@ type StrommixRaw = {
   measured_at_unix?: number | null;
 };
 
-/**
- * Fetch Energy-Charts /public_power directly with an explicit time
- * window. The CMS-cached `strommix_de` schema cannot do this because
- * external-collections v1 has no runtime-vars; without start/end the
- * upstream returns 404 ("no content available"). 2-hour window covers
- * latest 8 quarter-hour slots; we pick the latest non-null per series.
- */
 type PublicPowerSeries = { name: string; data: (number | null)[] };
 type PublicPowerResp = {
   unix_seconds?: number[];
@@ -67,25 +60,33 @@ function lastNonNull(arr: (number | null)[]): number | null {
   return null;
 }
 
+/**
+ * Fetch Energy-Charts /public_power with an explicit time window.
+ * `fromSec` is the window start (pass `dayStartSec` to cover all of today).
+ * Returns both the current-snapshot values (for live numbers) and the raw
+ * series (for the today-hourly sparkline when the history backend is empty).
+ */
 async function fetchEnergyChartsPublicPower(
-  fetcher: typeof fetch
+  fetcher: typeof fetch,
-): Promise<{ data: StrommixRaw | null; stale: boolean }> {
+  fromSec: number
+): Promise<{ data: StrommixRaw | null; rawSeries: PublicPowerResp | null; stale: boolean }> {
   try {
     const nowSec = Math.floor(Date.now() / 1000);
     const fmt = (sec: number) =>
       new Date(sec * 1000).toISOString().slice(0, 16) + "Z";
-    const start = fmt(nowSec - 2 * 60 * 60);
+    const start = fmt(fromSec);
     const end = fmt(nowSec);
     const url =
       `https://api.energy-charts.info/public_power?country=de` +
       `&start=${encodeURIComponent(start)}&end=${encodeURIComponent(end)}`;
     const res = await fetcher(url, { signal: AbortSignal.timeout(8_000) });
-    if (!res.ok) return { data: null, stale: false };
+    if (!res.ok) return { data: null, rawSeries: null, stale: false };
     const d = (await res.json()) as PublicPowerResp;
     const find = (n: string) =>
       d.production_types?.find((p) => p.name === n)?.data ?? [];
     const ts = d.unix_seconds ?? [];
     return {
+      rawSeries: d,
       data: {
         wind_onshore_mw: lastNonNull(find("Wind onshore")),
         wind_offshore_mw: lastNonNull(find("Wind offshore")),
@@ -102,10 +103,36 @@ async function fetchEnergyChartsPublicPower(
       stale: false,
     };
   } catch {
-    return { data: null, stale: true };
+    return { data: null, rawSeries: null, stale: true };
   }
 }
 
+/** Build today's sparkline series directly from an Energy-Charts response.
+ *  Used as fallback when the CMS history backend has no data yet. */
+function buildTodayHourlyFromEC(
+  d: PublicPowerResp,
+  dayStartSec: number
+): ResidualLoadPoint[] {
+  const ts = d.unix_seconds ?? [];
+  const find = (n: string) =>
+    d.production_types?.find((p) => p.name === n)?.data ?? [];
+  const load = find("Load");
+  const wOn = find("Wind onshore");
+  const wOff = find("Wind offshore");
+  const sol = find("Solar");
+  const result: ResidualLoadPoint[] = [];
+  for (let i = 0; i < ts.length; i++) {
+    if (ts[i] < dayStartSec) continue;
+    if (load[i] == null) continue;
+    result.push({
+      unix: ts[i],
+      loadMw: num(load[i]),
+      weatherRenewableMw: num(wOn[i]) + num(wOff[i]) + num(sol[i]),
+    });
+  }
+  return result.sort((a, b) => a.unix - b.unix);
+}
+
 type CrossborderRaw = {
   flow_at_gw?: number | null;
   flow_be_gw?: number | null;
@@ -501,10 +528,10 @@ export const GET: RequestHandler = async ({ fetch }) => {
   ] = await Promise.all([
     fetchSmardSnapshot(fetch),
     // Energy-Charts /public_power direct (with explicit time range —
-    // upstream now returns 404 without start/end). Used as per-field
+    // upstream returns 404 without start/end). Window starts at midnight so
-    // fallback when SMARD's load filter (id 410) lags 12+ hours behind
+    // the full-day series doubles as the sparkline fallback when the CMS
-    // the production filters and the SMARD snapshot gets discarded.
+    // history backend is empty. Used as per-field fallback when SMARD lags.
-    fetchEnergyChartsPublicPower(fetch),
+    fetchEnergyChartsPublicPower(fetch, dayStartSec),
     fetchOne<CrossborderRaw>("crossborder_de", fetch),
     fetchPriceAtNow("DE-LU", fetch),
     fetchPriceAtNow("FR", fetch),
@@ -599,9 +626,14 @@ export const GET: RequestHandler = async ({ fetch }) => {
   // Historical aggregates derived from CMS `_history`. `null` when the
   // backing collection is unavailable (e.g. CMS not yet upgraded with
   // history-mode schemas) — widget renders without the affected panels.
+  // Build today's sparkline series. Prefer the CMS history backend (full
+  // deduped timeline); fall back to the Energy-Charts direct response when
+  // history is empty (e.g. backfill not yet run on a fresh install).
   const todayHourly =
     histStrommix && histStrommix.items.length > 0
       ? buildTodayHourly(histStrommix.items)
+      : energyCharts.rawSeries
+        ? buildTodayHourlyFromEC(energyCharts.rawSeries, dayStartSec)
         : null;
   const negPriceHoursYtd = histPriceDe ? countNegPriceSlots(histPriceDe.items) : null;
   const crossborderYtd = histCrossborder