fix: respect SMTP encryption setting for email notifications

[sharkcreep87]

Summary

• Fixes the SMTP encryption setting being ignored when sending emails (test emails and all notifications)
• Symfony's EsmtpTransport constructor expects bool|null for the TLS parameter, but the code was passing incorrect values:
  • 'none' mapped to null (auto-detect) which still attempted STARTTLS — now correctly maps to false
  • 'tls' mapped to the string 'tls' instead of boolean true — now correctly maps to true

Encryption Setting	Before (broken)	After (fixed)	Symfony behavior
starttls	null	null (unchanged)	Try STARTTLS if supported
tls	'tls' (string)	true (bool)	Force implicit TLS
none	null (auto-detect)	false (disabled)	No encryption at all

Fixes #6442

Changes

File	Change
app/Notifications/Channels/EmailChannel.php	Fix match expression to return correct bool|null values for EsmtpTransport

Test plan

• Configure SMTP with Encryption set to "None" (port 25) → Send Test Email → verify it succeeds without attempting STARTTLS
• Configure SMTP with Encryption set to "TLS" (port 465) → Send Test Email → verify it connects with implicit TLS
• Configure SMTP with Encryption set to "STARTTLS" (port 587) → Send Test Email → verify STARTTLS upgrade works
• Verify team invitation emails also respect the encryption setting

[sharkcreep87]

Self-review — the fix aligns with Symfony's EsmtpTransport constructor signature (bool|null $tls):

Setting	Before (broken)	After (fixed)	Symfony behavior
starttls	null	null (no change)	Opportunistic STARTTLS
tls	'tls' (string)	true (bool)	Force implicit TLS
none	null (auto-detect)	false (disabled)	No encryption

The 'none' => null mapping was the direct cause — null tells Symfony to auto-detect and attempt STARTTLS, which fails on servers that don't support it.