fix(auth): return to origin path after GitHub login

Sign-in saves the current path in sessionStorage so the OAuth callback
can route back instead of always landing on Home.

src/components/SignInGithub.vue

@@ -1,20 +1,34 @@
 <script lang="ts" setup>
+import { useRoute } from "vue-router"
+
+import { GITHUB_OAUTH_RETURN_PATH_KEY } from "@/modules/user/service/oauthReturnPath"
+
 const GITHUB_URL = "https://github.com/login/oauth/authorize"
 
 const CLIENT_ID = "Iv1.12dc43d013ce3623"
 const SCOPE = "repo%20workflow"
 const REDIRECT_URI = window.location.origin
 
+const route = useRoute()
+
 const url = new URL(GITHUB_URL)
 url.searchParams.set("client_id", CLIENT_ID)
 url.searchParams.set("scope", SCOPE)
 url.searchParams.set("redirect_uri", REDIRECT_URI)
 
 const href = url.toString()
+
+const saveReturnPath = () => {
+  sessionStorage.setItem(GITHUB_OAUTH_RETURN_PATH_KEY, route.fullPath)
+}
 </script>
 
 <template>
-  <a :href="href" class="sign-in-github btn btn-sm btn-primary">
+  <a
+    :href="href"
+    class="sign-in-github btn btn-sm btn-primary"
+    @click="saveReturnPath"
+  >
     Sign in with
     <svg
       xmlns="http://www.w3.org/2000/svg"