docs(js): Quick Start guides: Auth tokens in env files (#14159)

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delete any sections you don't need. -->

In this PR, I've updated the Source Maps section in the Quick Start
guides (manual setup) to ensure we recommend storing the Sentry auth
token in an environment file instead of directly in the config files.

Updated for SDKs:
- Nuxt
- React Router Framework
- Solidstart  

Closes: #13896

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## PRE-MERGE CHECKLIST

*Make sure you've checked the following before merging your changes:*

- [ ] Checked Vercel preview for correctness, including links
- [ ] PR was reviewed and approved by any necessary SMEs (subject matter
experts)
- [ ] PR was reviewed and approved by a member of the [Sentry docs
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## EXTRA RESOURCES

- [Sentry Docs contributor guide](https://docs.sentry.io/contributing/)
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
- - - - - -

Author: inventarSarah

docs/platforms/javascript/guides/nextjs/manual-setup.mdx

@@ -16,7 +16,13 @@ description: "Learn how to manually set up Sentry in your Next.js app and captur
 Choose the features you want to configure, and this guide will show you how:
 
 <OnboardingOptionButtons
-  options={["error-monitoring", "performance", "session-replay", "user-feedback", "logs"]}
+  options={[
+    "error-monitoring",
+    "performance",
+    "session-replay",
+    "user-feedback",
+    "logs",
+  ]}
 />
 
 <PlatformContent includePath="getting-started-features-expandable" />
@@ -90,6 +96,7 @@ export default withSentryConfig(nextConfig, {
 ### Initialize Sentry Client-Side and Server-Side SDKs
 
 Create three files in your application's root directory:
+
 - `sentry.server.config.(js|ts)`
 - `sentry.edge.config.(js|ts)`
 - `instrumentation-client.(js|ts)`
@@ -220,7 +227,8 @@ Sentry.init({
 ```
 
 <Alert title="Tip">
-  Include your DSN directly in these files, or use a _public_ environment variable like `NEXT_PUBLIC_SENTRY_DSN`.
+  Include your DSN directly in these files, or use a _public_ environment
+  variable like `NEXT_PUBLIC_SENTRY_DSN`.
 </Alert>
 
 ### Register Sentry Server-Side SDK Initialization
@@ -433,7 +441,7 @@ module.exports = withSentryConfig(nextConfig, {
 });
 ```
 
-Alternatively, set the `SENTRY_AUTH_TOKEN` environment variable in your `.env` file:
+Set the `SENTRY_AUTH_TOKEN` environment variable in your `.env` file:
 
 ```sh {filename:.env}
 SENTRY_AUTH_TOKEN=___ORG_AUTH_TOKEN___

docs/platforms/javascript/guides/nuxt/manual-setup.mdx

@@ -51,7 +51,13 @@ Add the following overrides:
 Choose the features you want to configure, and this guide will show you how:
 
 <OnboardingOptionButtons
-  options={["error-monitoring", "performance", "session-replay", "user-feedback", "logs"]}
+  options={[
+    "error-monitoring",
+    "performance",
+    "session-replay",
+    "user-feedback",
+    "logs",
+  ]}
 />
 
 <PlatformContent includePath="getting-started-features-expandable" />
@@ -218,20 +224,29 @@ Check out the <PlatformLink to="/install/cli-import">`--import` CLI flag</Platfo
 
 To upload source maps for clear error stack traces, add your Sentry auth token, organization, and project slugs in the `sentry.sourceMapsUploadOptions` inside your configuration file:
 
-```javascript {filename:nuxt.config.ts} {3-9}
+<Alert>These `sentry` options only affect the **build time** of the SDK.</Alert>
+
+```javascript {filename:nuxt.config.ts} {3-10}
 export default defineNuxtConfig({
   modules: ["@sentry/nuxt/module"],
   sentry: {
     sourceMapsUploadOptions: {
       org: "___ORG_SLUG___",
       project: "___PROJECT_SLUG___",
-      authToken: "___ORG_AUTH_TOKEN___",
+      // store your auth token in an environment variable
+      authToken: process.env.SENTRY_AUTH_TOKEN,
     },
   },
 });
 ```
 
-<Alert>These `sentry` options only affect the **build time** of the SDK.</Alert>
+To keep your auth token secure, always store it in an environment variable instead of directly in your files:
+
+<OrgAuthTokenNote />
+
+```bash {filename:.env}
+SENTRY_AUTH_TOKEN=___ORG_AUTH_TOKEN___
+```
 
 While Nuxt generates source maps on the server side by default, you need to explicitly enable client-side source maps in your Nuxt configuration: