[Task] Database should require PG_ENCRYPT_KEY and bail out if none provided

[andrewazores]

Describe the feature

For data safety and integrity, the cryostat3-db image should require the user provide the PG_ENCRYPT_KEY environment variable used for encrypting the JMX credentials keyring. There should be no default value, so that the user or deployment system is forced to make this choice and provide an encryption key.

Anything other information?

No response