Fix E2E select locator and add speed limit color mode

E2E fixes:
- Color mode select locator now uses option[value='highway'] filter
  instead of fragile page.locator("select").last()

Speed limit color mode:
- Extract maxspeed tags from BRouter tiledesc (with forward/backward
  direction handling following brouter-web's pattern)
- Color route and chart by speed limit: green ≤30, yellow ≤50,
  orange ≤70, red ≤100, dark red 100+ km/h
- Legend with speed thresholds, hover shows "X km/h"
- i18n: EN "Speed Limit" / DE "Tempolimit"
- Mock fixtures include maxspeed data

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",
     },