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>

packages/i18n/src/locales/de.ts

@@ -103,6 +103,7 @@ export default {
       surface: "Untergrund",
       grade: "Steigung",
       highway: "Straßentyp",
+      maxspeed: "Tempolimit",
       surfaceLegend: "Farbe nach Straßenbelag",
       surfaceUnavailable: "Untergrunddaten für dieses Profil nicht verfügbar",
     },
@@ -113,6 +114,7 @@ export default {
       profile: "Höhenprofil",
       grade: "Steigungsprofil",
       highway: "Straßentypenprofil",
+      maxspeed: "Tempolimitprofil",
       low: "Tief",
       high: "Hoch",
     },

packages/i18n/src/locales/en.ts

@@ -103,6 +103,7 @@ export default {
       surface: "Surface",
       grade: "Grade",
       highway: "Road Type",
+      maxspeed: "Speed Limit",
       surfaceLegend: "Color by road surface type",
       surfaceUnavailable: "Surface data not available for this profile",
     },
@@ -113,6 +114,7 @@ export default {
       profile: "Elevation Profile",
       grade: "Grade Profile",
       highway: "Road Type Profile",
+      maxspeed: "Speed Limit Profile",
       low: "Low",
       high: "High",
     },