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_en.arb

@@ -300,6 +300,90 @@
   "loopFormSave": "Set up the band",
   "homeWorkouts": "Workouts",
   "homeDays": "Days",
+  "homePlans": "Plans",
+  "plansNew": "New plan",
+  "plansNewEmpty": "From nothing",
+  "plansEmptyTitle": "No plans yet",
+  "plansEmptyHint": "A plan's steps lead you through intervals as you record, with a tone, a vibration and a voice at each change. Start from a template, or from nothing.",
+  "planLocked": "A plan that doesn't open here",
+  "planTemplateFourByFour": "4×4 minutes",
+  "planTemplateTabata": "Tabata",
+  "planTemplateFourHundreds": "10×400 m",
+  "planTitle": "Plan",
+  "planNewTitle": "New plan",
+  "planName": "Name",
+  "planActivity": "For",
+  "planActivityAny": "Any activity",
+  "planOffTarget": "Tell me when I'm off target",
+  "planOffTargetHint": "A short cue at most every 30 seconds.",
+  "planSave": "Save",
+  "planNotSaved": "The plan wasn't saved.",
+  "planAddStep": "Add a step",
+  "planAddRepeat": "Add a repeat",
+  "planRepeat": "{count}×",
+  "@planRepeat": {"placeholders": {"count": {"type": "int"}}},
+  "planFewer": "Fewer rounds",
+  "planMore": "More rounds",
+  "planBlockMenu": "More",
+  "planMoveUp": "Move up",
+  "planMoveDown": "Move down",
+  "planRemove": "Remove",
+  "planDelete": "Delete",
+  "planDeleteTitle": "Delete this plan?",
+  "planDeleteMessage": "It's deleted on all your devices; workouts recorded with it keep their steps.",
+  "planDeleted": "Plan deleted",
+  "planSteps": "{count, plural, =1{1 step} other{{count} steps}}",
+  "@planSteps": {"placeholders": {"count": {"type": "int"}}},
+  "stepTitle": "Step",
+  "stepKind": "Kind",
+  "stepWarmUp": "Warm-up",
+  "stepWork": "Work",
+  "stepRecovery": "Recovery",
+  "stepCoolDown": "Cool-down",
+  "stepEnds": "Ends",
+  "stepEndTime": "After a time",
+  "stepEndDistance": "After a distance",
+  "stepEndLap": "With a lap tap",
+  "stepTimeLabel": "Time (min:s)",
+  "stepMetresLabel": "Metres",
+  "stepTarget": "Target",
+  "stepZone": "Zone",
+  "stepDone": "Done",
+  "stepMinutes": "{minutes} min",
+  "@stepMinutes": {"placeholders": {"minutes": {"type": "int"}}},
+  "stepSeconds": "{seconds} s",
+  "@stepSeconds": {"placeholders": {"seconds": {"type": "int"}}},
+  "stepMinutesSeconds": "{minutes} min {seconds} s",
+  "@stepMinutesSeconds": {"placeholders": {"minutes": {"type": "int"}, "seconds": {"type": "int"}}},
+  "stepMetres": "{metres} m",
+  "@stepMetres": {"placeholders": {"metres": {"type": "int"}}},
+  "stepKilometres": "{km} km",
+  "@stepKilometres": {"placeholders": {"km": {"type": "String"}}},
+  "stepUntilLap": "until a lap tap",
+  "targetNone": "None",
+  "targetFrom": "From",
+  "targetTo": "To",
+  "targetKindPace": "Pace (per km)",
+  "targetKindSpeed": "Speed (km/h)",
+  "targetKindHeartRate": "Heart rate (bpm)",
+  "targetKindHeartZone": "Heart-rate zone",
+  "targetKindSplit": "Split (per 500 m)",
+  "targetKindWatts": "Power (W)",
+  "targetKindStrokeRate": "Stroke rate (per min)",
+  "targetPace": "{from}–{to} per km",
+  "@targetPace": {"placeholders": {"from": {"type": "String"}, "to": {"type": "String"}}},
+  "targetSpeed": "{from}–{to} km/h",
+  "@targetSpeed": {"placeholders": {"from": {"type": "String"}, "to": {"type": "String"}}},
+  "targetHeartRate": "{from}–{to} bpm",
+  "@targetHeartRate": {"placeholders": {"from": {"type": "String"}, "to": {"type": "String"}}},
+  "targetZone": "Zone {zone}",
+  "@targetZone": {"placeholders": {"zone": {"type": "int"}}},
+  "targetSplit": "{from}–{to} per 500 m",
+  "@targetSplit": {"placeholders": {"from": {"type": "String"}, "to": {"type": "String"}}},
+  "targetWatts": "{from}–{to} W",
+  "@targetWatts": {"placeholders": {"from": {"type": "String"}, "to": {"type": "String"}}},
+  "targetStrokeRate": "{from}–{to} strokes/min",
+  "@targetStrokeRate": {"placeholders": {"from": {"type": "String"}, "to": {"type": "String"}}},
   "daysEmptyTitle": "No days yet",
   "daysEmptyHint": "The days and nights your Polar Loop counts show here.",
   "daysSteps": "{steps, plural, =1{1 step} other{{steps} steps}}",