docs: add Let's Encrypt email configuration note

[hamzainayat20]

What does this PR do?

Adds a note to the manual installation documentation explaining that the _APP_EMAIL_CERTIFICATE environment variable should be set before starting Appwrite when using Let's Encrypt.

Why?

Without this value, Let's Encrypt cannot issue SSL certificates. This note helps users avoid a common configuration issue during self-hosted installations.

Closes #2698

[greptile-apps]

Greptile Summary

This PR adds Let's Encrypt guidance to the manual self-hosting installation page. The main change is:

• An info box describing the certificate email configuration required before startup.

Confidence Score: 4/5

The certificate configuration note names an unused variable and needs correction before merging.

• The singular _APP_EMAIL_CERTIFICATE setting is not recognized by the installation configuration.
• Existing certificate configuration uses _APP_SYSTEM_SECURITY_EMAIL_ADDRESS for the issuance email.

src/routes/docs/advanced/self-hosting/installation/+page.markdoc

Important Files Changed

Filename	Overview
src/routes/docs/advanced/self-hosting/installation/+page.markdoc	Adds a Let's Encrypt setup note, but names an environment variable that the installation configuration does not use.

Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 1
src/routes/docs/advanced/self-hosting/installation/+page.markdoc:142
**Certificate Email Variable Is Ignored**

The manual installation configuration does not recognize the singular `_APP_EMAIL_CERTIFICATE` name. An installer following this note will set an unused variable while the certificate email remains unchanged, so the note does not prevent the certificate issue it describes.

```suggestion
If you plan to use Let's Encrypt for SSL certificates, make sure the `_APP_SYSTEM_SECURITY_EMAIL_ADDRESS` environment variable in your `appwrite/.env` file is set to a valid email address before starting Appwrite.
```

_{Reviews (1): Last reviewed commit: "docs: add Let's Encrypt email configurat..." | Re-trigger Greptile}

[greptile-apps]

Certificate Email Variable Is Ignored

The manual installation configuration does not recognize the singular _APP_EMAIL_CERTIFICATE name. An installer following this note will set an unused variable while the certificate email remains unchanged, so the note does not prevent the certificate issue it describes.

Suggested change

	If you plan to use Let's Encrypt for SSL certificates, make sure the `_APP_EMAIL_CERTIFICATE` environment variable in your `appwrite/.env` file is set to a valid email address before starting Appwrite. Without this value, Let's Encrypt certificates cannot be issued.
	If you plan to use Let's Encrypt for SSL certificates, make sure the `_APP_SYSTEM_SECURITY_EMAIL_ADDRESS` environment variable in your `appwrite/.env` file is set to a valid email address before starting Appwrite.

Prompt To Fix With AI

This is a comment left during a code review.
Path: src/routes/docs/advanced/self-hosting/installation/+page.markdoc
Line: 142

Comment:
**Certificate Email Variable Is Ignored**

The manual installation configuration does not recognize the singular `_APP_EMAIL_CERTIFICATE` name. An installer following this note will set an unused variable while the certificate email remains unchanged, so the note does not prevent the certificate issue it describes.

```suggestion
If you plan to use Let's Encrypt for SSL certificates, make sure the `_APP_SYSTEM_SECURITY_EMAIL_ADDRESS` environment variable in your `appwrite/.env` file is set to a valid email address before starting Appwrite.
```

How can I resolve this? If you propose a fix, please make it concise.