feat(train): interval plans, synced and sealed, with an editor and templates (ADR 0030, D42)

Train's server gains the synced `plan` table, a sealed payload alone;
the migration `plans` only adds it, its space index and the foreign key
to its sync space, and a person's deletion takes it with their space.

The app keeps plans as `plan` rows sealed for their row: a name, what
they are for, whether a step off target is told, and blocks of steps
repeated, each ending after a time, a distance or a lap tap and aiming
at a pace, speed, heart rate or zone, or the rower's split, watts or
stroke rate. Home's Plans tab lists them, a new one starts from nothing
or from a template (4×4 minutes, Tabata, 10×400 m), the editor changes
steps on a sheet, and a deletion asks first and can be undone.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/train/halkyon_train_flutter/lib/l10n/app_de.arb

@@ -241,6 +241,76 @@
   "loopFormSave": "Band einrichten",
   "homeWorkouts": "Workouts",
   "homeDays": "Tage",
+  "homePlans": "Pläne",
+  "plansNew": "Neuer Plan",
+  "plansNewEmpty": "Leer",
+  "plansEmptyTitle": "Noch keine Pläne",
+  "plansEmptyHint": "Die Schritte eines Plans führen dich beim Aufzeichnen durch Intervalle, mit Ton, Vibration und Stimme bei jedem Wechsel. Beginne mit einer Vorlage oder leer.",
+  "planLocked": "Ein Plan, der sich hier nicht öffnet",
+  "planTemplateFourByFour": "4×4 Minuten",
+  "planTemplateTabata": "Tabata",
+  "planTemplateFourHundreds": "10×400 m",
+  "planTitle": "Plan",
+  "planNewTitle": "Neuer Plan",
+  "planName": "Name",
+  "planActivity": "Für",
+  "planActivityAny": "Jede Aktivität",
+  "planOffTarget": "Sagen, wenn ich vom Ziel abweiche",
+  "planOffTargetHint": "Ein kurzer Hinweis, höchstens alle 30 Sekunden.",
+  "planSave": "Speichern",
+  "planNotSaved": "Der Plan wurde nicht gespeichert.",
+  "planAddStep": "Schritt hinzufügen",
+  "planAddRepeat": "Wiederholung hinzufügen",
+  "planRepeat": "{count}×",
+  "planFewer": "Weniger Runden",
+  "planMore": "Mehr Runden",
+  "planBlockMenu": "Mehr",
+  "planMoveUp": "Nach oben",
+  "planMoveDown": "Nach unten",
+  "planRemove": "Entfernen",
+  "planDelete": "Löschen",
+  "planDeleteTitle": "Diesen Plan löschen?",
+  "planDeleteMessage": "Er wird auf all deinen Geräten gelöscht; Trainings, die mit ihm aufgezeichnet wurden, behalten ihre Schritte.",
+  "planDeleted": "Plan gelöscht",
+  "planSteps": "{count, plural, =1{1 Schritt} other{{count} Schritte}}",
+  "stepTitle": "Schritt",
+  "stepKind": "Art",
+  "stepWarmUp": "Aufwärmen",
+  "stepWork": "Belastung",
+  "stepRecovery": "Erholung",
+  "stepCoolDown": "Auslaufen",
+  "stepEnds": "Endet",
+  "stepEndTime": "Nach einer Zeit",
+  "stepEndDistance": "Nach einer Strecke",
+  "stepEndLap": "Mit der Rundentaste",
+  "stepTimeLabel": "Zeit (min:s)",
+  "stepMetresLabel": "Meter",
+  "stepTarget": "Ziel",
+  "stepZone": "Zone",
+  "stepDone": "Fertig",
+  "stepMinutes": "{minutes} min",
+  "stepSeconds": "{seconds} s",
+  "stepMinutesSeconds": "{minutes} min {seconds} s",
+  "stepMetres": "{metres} m",
+  "stepKilometres": "{km} km",
+  "stepUntilLap": "bis zur Rundentaste",
+  "targetNone": "Keins",
+  "targetFrom": "Von",
+  "targetTo": "Bis",
+  "targetKindPace": "Tempo (pro km)",
+  "targetKindSpeed": "Geschwindigkeit (km/h)",
+  "targetKindHeartRate": "Herzfrequenz (Schläge/min)",
+  "targetKindHeartZone": "Herzfrequenzzone",
+  "targetKindSplit": "Split (pro 500 m)",
+  "targetKindWatts": "Leistung (W)",
+  "targetKindStrokeRate": "Schlagzahl (pro min)",
+  "targetPace": "{from}–{to} pro km",
+  "targetSpeed": "{from}–{to} km/h",
+  "targetHeartRate": "{from}–{to} Schläge/min",
+  "targetZone": "Zone {zone}",
+  "targetSplit": "{from}–{to} pro 500 m",
+  "targetWatts": "{from}–{to} W",
+  "targetStrokeRate": "{from}–{to} Schläge/min",
   "daysEmptyTitle": "Noch keine Tage",
   "daysEmptyHint": "Die Tage und Nächte, die dein Polar Loop zählt, erscheinen hier.",
   "daysSteps": "{steps, plural, =1{1 Schritt} other{{steps} Schritte}}",