refactor(secrets): remove migrate_encrypt command

Made-with: Cursor

src/db.rs

@@ -37,8 +37,7 @@ pub async fn migrate(pool: &PgPool) -> Result<()> {
 
         -- Migrate encrypted column from JSONB to BYTEA if still JSONB type.
         -- After migration, old plaintext rows will have their JSONB data
-        -- stored as raw bytes (not yet re-encrypted); run `secrets migrate-encrypt`
-        -- to encrypt them with the master key.
+        -- stored as raw bytes (UTF-8 encoded).
         DO $$ BEGIN
             IF EXISTS (
                 SELECT 1 FROM information_schema.columns