fix: remove duplicate headers, fix i18n keys, unify theme colors in Discover and Schedules views

- DiscoverView: removed internal header (duplicate of AppHeader), replaced Tailwind hardcoded colors with CSS theme variables (--bg-primary, --active-color, etc.)
- SchedulesView: removed internal header (duplicate of AppHeader), replaced Tailwind hardcoded colors with CSS theme variables
- es.json: add missing keys discover.searchPlaceholder, schedules.placeholder, schedules.upcoming, schedules.noSchedules, schedules.types
- en.json: same missing keys added for English

frontend/src/i18n/locales/en.json

@@ -70,10 +70,18 @@
     "loadingRoutes": "Loading routes...",
     "noRoutesAvailable": "No routes available",
     "selectRoute": "Select a route",
+    "placeholder": "Choose a route...",
+    "upcoming": "Upcoming departures",
+    "noSchedules": "No departures scheduled for today",
     "route": "Route",
     "schedules": "schedules",
     "schedule": "schedule",
-    "departureTime": "Departure time"
+    "departureTime": "Departure time",
+    "types": {
+      "weekday": "Weekday",
+      "weekend": "Weekend",
+      "holiday": "Holiday"
+    }
   },
   "coupons": {
     "title": "Offers",
@@ -134,6 +142,7 @@
   "discover": {
     "title": "Discover",
     "subtitle": "Explore the best places in Chiriqui",
+    "searchPlaceholder": "Explore the best places in Chiriqui",
     "filterLabel": "Filter by area:",
     "allAreas": "All",
     "loading": "Searching for treasures...",