Metro map interaction redesign: fit-to-view zoom, grid, branch handles, custom tracks

Phase 1 — Fit-to-view zoom:
- computeFitTransform() calculates bounding box and scales to fit all nodes
- Replaces hardcoded scale=1 reset in animateZoomReset() and initCanvas()
- Dim 1 no longer appears tiny after zooming out from dim 2

Phase 2 — Grid system:
- Shared gridConstants.js (GRID=50, GRID_STEP_X=200, GRID_STEP_Y=150)
- MapDataService snapToGrid() aligns all node positions server-side
- Canvas renders subtle grid lines (shown on interaction only, with fade)
- Line highlighting support via setHighlightedLine() for FAB hover

Phase 3 — Branch handles:
- Hover any station node → 3 "+" handles appear (0°/45°/315°)
- 0° extends the current line, 45°/315° fork to create new branch
- Ghost preview (dashed line + circle) on handle hover
- Handles only show at unoccupied grid positions
- Grid fades in during handle interaction, fades out after

Phase 4 — Custom tracks database:
- metro_lines table (project_id, naam, color, type, order)
- metro_nodes table (metro_line_id, naam, status, x, y, order)
- MetroLine + MetroNode models, controllers, routes
- Project.metroLines() relationship added

Phase 5+6 — FAB redesign + MetroMap wiring:
- FAB shows "Nieuw thema (lijn)" at root, "Nieuwe lijn" in project dim
- Track creation modal with retro-styled form
- MetroMap handles create-node events from branch handles
- Extend (0°) opens commitment/document form, fork opens track form
- Canvas context menu replaced with "hover to branch" hint

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

app/Http/Controllers/MetroNodeController.php

@@ -0,0 +1,51 @@
+<?php
+
+namespace App\Http\Controllers;
+
+use App\Models\MetroNode;
+use Illuminate\Http\Request;
+
+class MetroNodeController extends Controller
+{
+    public function store(Request $request)
+    {
+        $validated = $request->validate([
+            'metro_line_id' => 'required|exists:metro_lines,id',
+            'naam'          => 'required|string|max:255',
+            'beschrijving'  => 'nullable|string',
+            'x'             => 'required|integer',
+            'y'             => 'required|integer',
+            'eigenaar_id'   => 'nullable|exists:users,id',
+        ]);
+
+        $maxOrder = MetroNode::where('metro_line_id', $validated['metro_line_id'])->max('order') ?? 0;
+        $validated['order'] = $maxOrder + 1;
+        $validated['status'] = 'active';
+
+        $node = MetroNode::create($validated);
+
+        return back()->with('success', "Node '{$node->naam}' aangemaakt.");
+    }
+
+    public function update(Request $request, MetroNode $metroNode)
+    {
+        $validated = $request->validate([
+            'naam'         => 'sometimes|string|max:255',
+            'beschrijving' => 'nullable|string',
+            'status'       => 'sometimes|string|in:active,completed,parked',
+            'x'            => 'sometimes|integer',
+            'y'            => 'sometimes|integer',
+        ]);
+
+        $metroNode->update($validated);
+
+        return back()->with('success', 'Node bijgewerkt.');
+    }
+
+    public function destroy(MetroNode $metroNode)
+    {
+        $metroNode->delete();
+
+        return back()->with('success', 'Node verwijderd.');
+    }
+}