[Docs] engine and ub changes (#7049)

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## PR-Codex overview
This PR focuses on enhancing the documentation and user guidance for the `thirdweb` platform, specifically around the Engine v3 features, onramp providers, and pricing details. It introduces new FAQs, clarifies migration steps, and adds visual content.

### Detailed summary
- Added new section for "Onramp Providers" in `sidebar.tsx`.
- Updated Engine FAQs in `page.mdx` with pricing and transaction details.
- Revised migration guide in `page.mdx` with clearer instructions and a callout for wallet migration.
- Enhanced `faqs/page.mdx` with additional questions about Universal Bridge and supported payment methods.
- Updated "Buy With Fiat" availability to 160+ countries.
- Included images for creating a vault and sending transactions in the `get-started/page.mdx`.
- Revised onramp providers section to clarify provider preferences and fees in `onramp-providers/page.mdx`.

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Author: saminacodes

apps/portal/src/app/connect/pay/faqs/page.mdx

@@ -29,6 +29,15 @@ This can include intents, native bridges, third party bridges, cross-chain messa
 health, price, and speed to guarantee the best path every time. 
 </Details>
 
+<Details summary="Am I able to use Universal Bridge with other wallet infrastructure providers?"> 
+Yes, Universal Bridge is designed to be agnostic to wallet infrastructure. You can use it with any wallet service. 
+</Details>
+
+
+<Details summary="Does Universal Bridge support Apple Pay or Google Pay?"> 
+Apple Pay and Google Pay are supported through the onramp providers depending on region. Coinbase, Stripe, and Transak currently support Apple Pay. Transak supports Google Pay. [Learn more about the supported onramp providers.](/connect/pay/onramp-providers).
+</Details>
+
 <Details summary="What are the KYC requirements?">
 Onramp options all require minimal KYC. This is done to comply with local regulations and to ensure the safety of our users.
 Please note: onramping with Coinbase does not require KYC for a purchase below $500 with debit card. 
@@ -41,7 +50,7 @@ Our transaction maximum starts from $1500 per week for new users and can increas
 </Details>
 
 <Details summary="What countries does Buy With Fiat support?"> 
-**Buy With Fiat** is available 130+ countries. The following countries are _UNSUPPORTED_:
+**Buy With Fiat** is available 160+ countries. The following countries are _UNSUPPORTED_:
 
 - Afghanistan
 - Africa (All Countries)

apps/portal/src/app/connect/pay/onramp-providers/page.mdx

@@ -12,14 +12,30 @@ export const metadata = createMetadata({
 
 # Onramp Providers
 
-thirdweb Universal Bridge integrates with Stripe, Kado and Transak to power our onramp. By default, we choose a recommended provider based on the location of the user, KYC status, and currency.
+**Onramp Providers** are services that allow users to buy crypto with fiat. You can set preferred providers for your application by using the [`preferredProvider`](/connect/pay/customization/payembed#preferred-provider) parameter in the `PayEmbed` component.
+Universal Bridge supports the following onramp providers:
 
-| Provider | Supported Countries                                                                                     |
-| -------- | ------------------------------------------------------------------------------------------------------- |
-| Transak  | https://transak.notion.site/On-Ramp-Payment-Methods-Fees-Other-Details-b0761634feed4b338a69f4f186d906a5 |
-| Kado     | https://www.kado.money/supported-countries                                                              |
-| Stripe   | https://docs.stripe.com/crypto/onramp                                                                   |
+- **Coinbase**
+- **Transak**
+- **Stripe**
 
-## Choosing a Preferred Provider
+## Provider Fees
 
-It is possible to specify a preferred onramp provider by setting the `preferredProvider` parameter in the ConnectButton, PayEmbed, or Headless Integration. Go to [customizations](../pay/customization/connectbutton#preferredProvider) for more detail, or checkout the [API Reference for preferredProvider](https://portal.thirdweb.com/references/typescript/v5/GetBuyWithFiatQuoteParams).
+Each provider has different fees associated with their services which often depend on various factors. Onramp provider fees are set by the provider and are not controlled by thirdweb.
+
+| Provider | Fees |
+| -------- | ---- |
+| Coinbase | [Learn more about Coinbase Fees](https://help.coinbase.com/en/coinbase/trading-and-funding/pricing-and-fees/fees) |
+| Transak  |  [Learn more about Transak Fees](https://support.transak.com/en/articles/7845942-how-does-transak-calculate-prices-and-fees)|
+| Stripe | [Learn more about Stripe Fees](https://stripe.com/legal/crypto-onramp). |
+
+
+## Provider Regions
+
+Each provider has different regions they support. You can learn more about the supported regions for each provider in the links below.
+
+| Provider | Regions |
+| -------- | ------- |
+| Coinbase | [View Regions](https://docs.cdp.coinbase.com/onramp/docs/api-configurations) |
+| Transak  | [View Regions](https://transak.com/global-coverage) |
+| Stripe  | [View Regions](https://support.stripe.com/questions/crypto-supportability-and-availability-by-region) |

apps/portal/src/app/connect/sidebar.tsx

@@ -241,6 +241,10 @@ export const sidebar: SideBar = {
           name: "Supported Routes",
           href: "https://thirdweb.com/routes",
         },
+        {
+          name: "Onramp Providers",
+          href: `${paySlug}/onramp-providers`,
+        },
         {
           name: "Service Fees",
           href: `${paySlug}/fees`,

apps/portal/src/app/engine/v3/assets/create-vault.png

@@ -2,4 +2,10 @@ import { Callout, Details } from "@doc";
 
 # Engine FAQs
 
-More information coming soon.
+<Details summary="How is pricing calculated for Engine Cloud?">
+Pricing is calculated through the number of write requests (ex: /v1/write/contract) made through the Engine API. Requests cost $1 per 1,000 requests. Read requests made through Engine API are free, within the RPC limits/plan. 
+
+For transactions completed through server wallets paid through the user's thirdweb account, users will pay a 5% premium on the gas fee of each transaction completed. 
+
+The breakdown for usage and transaction fees can be found in your usage dashboard under the team overview. 
+</Details>

apps/portal/src/app/engine/v3/assets/send-transaction.png

@@ -1,4 +1,6 @@
-import { Callout, Step, Steps, Tabs, TabsContent, TabsTrigger, TabsList } from "@doc";
+import { Callout, Step, Steps, Tabs, TabsContent, TabsTrigger, TabsList, DocImage } from "@doc";
+import CreateVault from '../assets/create-vault.png';
+import SendTransaction from '../assets/send-transaction.png';
 
 # Get started
 
@@ -19,7 +21,8 @@ Learn how to get started with thirdweb Engine. This guide will walk you through
 		Create a vault to manage your Engine's server wallets. After setup, you can manage your Vault to create additional access tokens or rotate admin keys.
 
 		<Callout variant="info" title="Vault">
-			Vault is thirdweb's key management service designed to store smart server wallets non-custodially. Learn more about [Vault].
+			Vault is thirdweb's key management service designed to store smart server wallets non-custodially. [Learn more about Vault.](/vault)
+			<DocImage src={CreateVault} alt="Create Vault"/>
 		</Callout>
 	</Step>
 
@@ -35,6 +38,7 @@ Learn how to get started with thirdweb Engine. This guide will walk you through
 		To verify your server wallet setup and see how transactions work, you can send a test transaction in the next step. This sends a no-op transaction—a transaction with zero value—to your own wallet.
 
 		You can send additional test transactions or proceed with the full setup whenever you're ready.
+		<DocImage src={SendTransaction} alt="Send Test Transaction"/>
 	</Step>
 
 	<Step title="Integrate with your app">

apps/portal/src/app/engine/v3/faq/page.mdx

@@ -1,6 +1,12 @@
+import { Callout } from "@doc";
+
 # Migrating from Engine v2 to v3
 
-This guide outlines the key changes required to migrate your applications from Engine v2 to Engine v3. We'll cover common operations and highlight the differences in API requests and authentication.
+Learn how to migrate your applications from Engine v2 to Engine v3. We'll cover common operations and highlight the differences in API requests and authentication.
+
+<Callout variant="info" title="Migrating Wallets">
+If you'd like to migrate your wallets from v2 to v3 to also be secured by [Vault](/vault) or thirdweb's key management service, please [contact us for assistance.](https://thirdweb.com/support) 
+</Callout>
 
 ## Writing to a contract