Rewarded videos ads to test a skin (#3120)

## Description:

Added rewarded video ads for skin trials via Playwire's
manuallyCreateRewardUi API. Users can now click "Try me" to watch a
video ad and receive a temporary skin trial. Upon completion a temporary
flare is granted to the player so they have ~5 minutes to use the skin.

added getPlayerCosmeticsRefs and getPlayerCosmetics to Cosmetics.ts to
centralize cosmetic retrieval & validation.

<img width="801" height="534" alt="Screenshot 2026-02-10 at 7 58 14 PM"
src="https://github.com/user-attachments/assets/51cc378c-2feb-4692-8cf2-20ee54cea3b8"
/>

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

## Please put your Discord username so you can be contacted if a bug or
regression is found:

evan

src/client/Api.ts

@@ -125,6 +125,31 @@ export async function createCheckoutSession(
   }
 }
 
+export async function grantTemporaryFlare(flare: string): Promise<boolean> {
+  try {
+    const response = await fetch(`${getApiBase()}/flares_granted/temporary`, {
+      method: "POST",
+      headers: {
+        "Content-Type": "application/json",
+        Authorization: await getAuthHeader(),
+      },
+      body: JSON.stringify({ flare }),
+    });
+    if (!response.ok) {
+      console.error(
+        "grantTemporaryFlare: request failed",
+        response.status,
+        response.statusText,
+      );
+      return false;
+    }
+    return true;
+  } catch (e) {
+    console.error("grantTemporaryFlare: request failed", e);
+    return false;
+  }
+}
+
 export function getApiBase() {
   const domainname = getAudience();