Re-add speed limit color mode with BRouter profile patch

The dummyUsage trick needs a separate assign per tag:
  assign dummyUsage2 = maxspeed=
(not appended to the existing smoothness= line)

- Dockerfile: Patch all BRouter profiles to include maxspeed in
  WayTags output via separate assign dummyUsage2
- brouter.ts: Extract maxspeed with direction handling
  (maxspeed:forward/backward + reversedirection awareness)
- ColoredRoute: maxspeed color mode (green ≤30, yellow ≤50,
  orange ≤70, red ≤100, dark red 100+)
- ElevationChart: maxspeed chart rendering, legend, hover "X km/h"
- PlannerMap: maxspeeds state + Yjs read + prop passing
- i18n: EN "Speed Limit" / DE "Tempolimit"
- Mock fixtures: maxspeed data for E2E tests

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

e2e/fixtures/brouter-mock.ts

@@ -40,6 +40,10 @@ const MOCK_ROUTE_3WP = {
     "residential", "residential", "cycleway", "cycleway", "path",
     "path", "tertiary", "tertiary", "residential", "residential",
   ],
+  maxspeeds: [
+    "30", "30", "unknown", "unknown", "unknown",
+    "unknown", "50", "50", "30", "30",
+  ],
 };
 
 /**
@@ -76,6 +80,9 @@ const MOCK_ROUTE_2WP = {
   highways: [
     "secondary", "secondary", "cycleway", "cycleway", "residential", "residential",
   ],
+  maxspeeds: [
+    "50", "50", "unknown", "unknown", "30", "30",
+  ],
 };
 
 /**