L2 Aufträge & Backoffice: Service-Schicht Aufträge + Tests

Statusmaschine (transitionWorkOrder inkl. eventData), Zuweisung, Completion-Guards,
Materialvorgabe, Checklisten/Pflichtfotos, Liste/Dashboard-Presets, Suche,
Sync-Konflikte, Einstellungen (Auftragsarten, Vorlagen, Nummernkreise).
Tests: Übergangsmatrix je Rolle, Kernlogik, Scope/Mandantentrennung, Nummernkreis-Parallelität.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/lib/work-orders/time.ts

@@ -0,0 +1,86 @@
+/**
+ * Timezone helpers (client-safe, Intl only). Planned dates are entered as wall-clock time in the
+ * tenant timezone (TenantSettings.timezone) and stored as UTC.
+ */
+
+export const DEFAULT_TIMEZONE = "Europe/Berlin";
+
+export function safeTimeZone(tz: string | null | undefined): string {
+  if (!tz) return DEFAULT_TIMEZONE;
+  try {
+    new Intl.DateTimeFormat("en-US", { timeZone: tz });
+    return tz;
+  } catch {
+    return DEFAULT_TIMEZONE;
+  }
+}
+
+/** Offset (ms) of `timeZone` relative to UTC at instant `at`. */
+export function tzOffsetMs(at: Date, timeZone: string): number {
+  const parts = new Intl.DateTimeFormat("en-US", {
+    timeZone,
+    hourCycle: "h23",
+    year: "numeric",
+    month: "2-digit",
+    day: "2-digit",
+    hour: "2-digit",
+    minute: "2-digit",
+    second: "2-digit",
+  }).formatToParts(at);
+  const n = (t: string) => Number(parts.find((p) => p.type === t)?.value);
+  const asUtc = Date.UTC(n("year"), n("month") - 1, n("day"), n("hour"), n("minute"), n("second"));
+  return asUtc - Math.floor(at.getTime() / 1000) * 1000;
+}
+
+/** "2026-09-14T08:30" (wall time in tz) → UTC Date. Returns undefined for invalid input. */
+export function wallTimeToUtc(value: string, timeZone: string): Date | undefined {
+  const m = /^(\d{4})-(\d{2})-(\d{2})(?:T(\d{2}):(\d{2}))?$/.exec(value.trim());
+  if (!m) return undefined;
+  const tz = safeTimeZone(timeZone);
+  const guess = Date.UTC(+m[1], +m[2] - 1, +m[3], m[4] ? +m[4] : 0, m[5] ? +m[5] : 0);
+  const first = guess - tzOffsetMs(new Date(guess), tz);
+  // second pass corrects DST boundaries
+  const result = guess - tzOffsetMs(new Date(first), tz);
+  const d = new Date(result);
+  return Number.isNaN(d.getTime()) ? undefined : d;
+}
+
+/** UTC Date → "YYYY-MM-DDTHH:mm" wall time in tz (for <input type="datetime-local">). */
+export function toWallTimeInput(date: Date | null | undefined, timeZone: string): string {
+  if (!date) return "";
+  const parts = new Intl.DateTimeFormat("en-CA", {
+    timeZone: safeTimeZone(timeZone),
+    hourCycle: "h23",
+    year: "numeric",
+    month: "2-digit",
+    day: "2-digit",
+    hour: "2-digit",
+    minute: "2-digit",
+  }).formatToParts(date);
+  const p = (t: string) => parts.find((x) => x.type === t)?.value ?? "00";
+  return `${p("year")}-${p("month")}-${p("day")}T${p("hour")}:${p("minute")}`;
+}
+
+/** Start/end of the calendar day containing `now` in the given timezone. */
+export function zonedDayBounds(now: Date, timeZone: string): { start: Date; end: Date } {
+  const tz = safeTimeZone(timeZone);
+  const [y, m, d] = new Intl.DateTimeFormat("en-CA", { timeZone: tz, year: "numeric", month: "2-digit", day: "2-digit" })
+    .format(now)
+    .split("-")
+    .map(Number);
+  const guessStart = Date.UTC(y, m - 1, d, 0, 0, 0);
+  const start = new Date(guessStart - tzOffsetMs(new Date(guessStart), tz));
+  const guessEnd = Date.UTC(y, m - 1, d, 23, 59, 59, 999);
+  const end = new Date(guessEnd - tzOffsetMs(new Date(guessEnd), tz));
+  return { start, end };
+}
+
+export function formatDateTime(date: Date | null | undefined, locale: string, timeZone: string): string {
+  if (!date) return "";
+  return new Intl.DateTimeFormat(locale === "en" ? "en-GB" : "de-DE", { timeZone: safeTimeZone(timeZone), dateStyle: "medium", timeStyle: "short" }).format(date);
+}
+
+export function formatDate(date: Date | null | undefined, locale: string, timeZone: string): string {
+  if (!date) return "";
+  return new Intl.DateTimeFormat(locale === "en" ? "en-GB" : "de-DE", { timeZone: safeTimeZone(timeZone), dateStyle: "medium" }).format(date);
+}