Implement active Location Sharing Stopped/Ended state with red dot pin

backend/src/main/java/com/rit/portal/controller/BusLocationController.java

@@ -37,6 +37,20 @@ public class BusLocationController {
         return ResponseEntity.ok(Map.of("status", "success", "message", "Location updated successfully"));
     }
 
+    @PostMapping("/{routeNumber}/stop")
+    public ResponseEntity<Map<String, String>> stopLocation(
+            @PathVariable String routeNumber,
+            @RequestBody Map<String, String> body) {
+        
+        String pin = body != null ? body.get("pin") : null;
+        if (!REQUIRED_PIN.equals(pin)) {
+            return ResponseEntity.status(HttpStatus.UNAUTHORIZED).body(Map.of("error", "Invalid driver PIN"));
+        }
+
+        busLocationService.stopLocation(routeNumber);
+        return ResponseEntity.ok(Map.of("status", "success", "message", "Location sharing stopped"));
+    }
+
     @GetMapping
     public ResponseEntity<List<BusLocation>> getActiveLocations() {
         return ResponseEntity.ok(busLocationService.getActiveLocations());

backend/src/main/java/com/rit/portal/model/BusLocation.java

@@ -13,4 +13,5 @@ public class BusLocation {
     private Double latitude;
     private Double longitude;
     private Instant lastUpdated;
+    private boolean stopped = false;
 }

backend/src/main/java/com/rit/portal/service/BusLocationService.java

@@ -19,10 +19,19 @@ public class BusLocationService {
             routeNumber,
             latitude,
             longitude,
-            Instant.now()
+            Instant.now(),
+            false
         ));
     }
 
+    public void stopLocation(String routeNumber) {
+        BusLocation loc = locationCache.get(routeNumber);
+        if (loc != null) {
+            loc.setStopped(true);
+            loc.setLastUpdated(Instant.now());
+        }
+    }
+
     public BusLocation getLocation(String routeNumber) {
         BusLocation loc = locationCache.get(routeNumber);
         if (loc != null) {