Fix env templateto ensure compatibility with systemd's EnvironmentFile parsing (#4315)

* fix: update env template for systemd compatibility

Adjust env template to ensure compatibility with systemd's EnvironmentFile parsing, which only recognizes line-starting comment symbols.

* Refactor SMTP and Rocket settings in .env.template

- Simplify the SMTP_SECURITY and SMTP_PORT options by providing a list of choices and default values
- Clarify the ROCKET_PORT default value depending on the environment (Docker or not)

.env.template

@@ -477,12 +477,19 @@
 # SMTP_HOST=smtp.domain.tld
 # SMTP_FROM=vaultwarden@domain.tld
 # SMTP_FROM_NAME=Vaultwarden
-# SMTP_SECURITY=starttls # ("starttls", "force_tls", "off") Enable a secure connection. Default is "starttls" (Explicit - ports 587 or 25), "force_tls" (Implicit - port 465) or "off", no encryption (port 25)
-# SMTP_PORT=587          # Ports 587 (submission) and 25 (smtp) are standard without encryption and with encryption via STARTTLS (Explicit TLS). Port 465 (submissions) is used for encrypted submission (Implicit TLS).
 # SMTP_USERNAME=username
 # SMTP_PASSWORD=password
 # SMTP_TIMEOUT=15
 
+## Choose the type of secure connection for SMTP. The default is "starttls".
+## The available options are:
+## - "starttls": The default port is 587.
+## - "force_tls": The default port is 465.
+## - "off": The default port is 25.
+## Ports 587 (submission) and 25 (smtp) are standard without encryption and with encryption via STARTTLS (Explicit TLS). Port 465 (submissions) is used for encrypted submission (Implicit TLS).
+# SMTP_SECURITY=starttls
+# SMTP_PORT=587
+
 # Whether to send mail via the `sendmail` command
 # USE_SENDMAIL=false
 # Which sendmail command to use. The one found in the $PATH is used if not specified.
@@ -524,7 +531,8 @@
 ## Rocket specific settings
 ## See https://rocket.rs/v0.5/guide/configuration/ for more details.
 # ROCKET_ADDRESS=0.0.0.0
-# ROCKET_PORT=80  # Defaults to 80 in the Docker images, or 8000 otherwise.
+## The default port is 8000, unless running in a Docker container, in which case it is 80.
+# ROCKET_PORT=8000
 # ROCKET_TLS={certs="/path/to/certs.pem",key="/path/to/key.pem"}