Give the Streckenplaner real track CRUD and a self-fitting layout

[Ktechen]

The 2D planner was a single hard-coded 8-segment stadium loop. It now builds arbitrary plans: append Gerade/Kurve/Weiche/Bahnhof, duplicate, reorder, delete, or start from an Oval/Acht/Punkt-zu-Punkt template, with a Weiche splitting the plan into a Stammgleis and its own branch strand that can be built on further.

Core:

• Domain gains CurveDirection/SwitchRoute and the strand/branch fields on TrackSegment; Application gains the pure TrackPlanService (append/insert-switch/ duplicate/reorder/delete/templates) behind ITrackPlanService, TrackSegmentDto + mapping, and ITrackSegmentRepository; Infrastructure persists segments via SqliteTrackSegmentRepository on the existing BaseRepository.
• Deleting a Weiche cascades through its branch, including nested Weichen.

Layout (Trackify/Helpers/TrackGeometry.cs) is now turtle graphics over the strand graph instead of a closed form, in two passes: the walk lays every strand out in unbounded world coordinates, then the emit pass bakes in the scale/offset that centers the finished plan on the 900x600 canvas and shrinks it (never enlarges) when it would reach into the margin the labels and sensor markers need. A plan can therefore grow in any direction without walking off the visible area — before, the walk started at a fixed (150,300) and the Oval sat in the left third.

Position fixes that came out of that:

• A curve's outward normal is derived from the tangent, like a straight's, instead of "away from the arc center" — the latter flips between left and right curves, so speed labels and sensor markers changed sides mid-plan.
• The direction arrow is emitted as path data (TrackSegment.ArrowPathData) rather than a triangle rotated by a bound RenderTransform: a {Binding} inside a transform has no DataContext to inherit — transforms aren't in the visual tree — so the angle never arrived, and the old geometry's negative coordinates left the arrow's origin up to the renderer.
• The Acht template's second lobe leads with its turn. Leading with straights, as the first lobe does, retraced its opening Gerade and Bahnhof piece-for-piece from the same anchor pose: two segments stacked at identical coordinates.
• A strand nothing branches into (a branch whose Weiche is gone, e.g. from a plan saved mid-write) is parked on its own lane below the plan instead of silently keeping the position it had in the previous layout.
• ApplyPlan computes the layout once instead of twice (segments + ballast path).

UI: the planner page is a splitter-resizable canvas / strand list / segment inspector, collapsing to a stacked layout with the inspector as a bottom sheet on narrow screens; zoom is a bound ZoomFactor driving a Viewbox, not a ScrollViewer call. New StrandList and BlueprintFrame, Column/RowSplitterBehavior, and refreshed design tokens and palette.

Verified: all four buildable Uno heads (desktop/windows/android/browserwasm), CLI, dotnet test (40 passing, incl. new TrackPlanServiceTests), desktop launch smoke test. The canvas itself cannot be pixel-verified in this environment, so the visuals still need a look on a real device.

[sonarqubecloud]

Quality Gate failed

Failed conditions
8.4% Duplication on New Code (required ≤ 3%)

See analysis details on SonarQube Cloud