Made 'Петроградская' default metro station

Related to #44

front/src/assets/metro.ts

@@ -105,5 +105,7 @@ const lineByName = (name: string) => (
     lines.find(line => stations[line].has(name))
 )
 
+const DEFAULT_LINE = 'Петроградская'
+
 export type { Lines }
-export { lines, stations, colors, lineNames, lineByName }
+export { lines, stations, colors, lineNames, lineByName, DEFAULT_LINE }

front/src/pages/AddPage.tsx

@@ -7,7 +7,7 @@ import { useNavigate } from 'react-router-dom'
 import { MapClickHandler, LocationMarker, CardLayout, LocateButton } from '../components'
 import { useAddAnnouncement } from '../hooks/api'
 import { categories, categoryNames } from '../assets/category'
-import { stations, lines, lineNames } from '../assets/metro'
+import { stations, lines, lineNames, DEFAULT_LINE } from '../assets/metro'
 import { fallbackError, gotResponse } from '../hooks/useFetch'
 import { useOsmAddresses } from '../hooks/api'
 
@@ -126,10 +126,7 @@ function AddPage() {
                     <Form.Label>
                         Станция метро
                     </Form.Label>
-                    <Form.Select name='metro'>
-                        <option value=''>
-                            Укажите ближайщую станцию метро
-                        </option>
+                    <Form.Select name='metro' defaultValue={DEFAULT_LINE}>
                         {lines.map(
                             line =>
                                 <optgroup key={line} label={lineNames[line]}>