feat: encrypt private keys saved on disk and in database (#682)

Co-authored-by: Kyle Mendell <kmendell@ofkm.us>

backend/internal/model/kv.go

@@ -0,0 +1,11 @@
+package model
+
+type KV struct {
+	Key   string `gorm:"primaryKey;not null"`
+	Value *string
+}
+
+// TableName overrides the table name used by KV to `kv`
+func (KV) TableName() string {
+	return "kv"
+}