feat(deploy): webhook queue+nocache, restart sweep, secrets at rest

- Webhook-triggered deploys now go through the per-service deploy queue
  and default to no_cache builds (dflow convention — prevents stale
  layer surprises on push).
- Boot sweep marks deployments interrupted by restart as failed instead
  of leaving phantom queued/building rows.
- is_secret environment variables are AES-GCM-encrypted at rest
  (enc:v1: prefix); key from SECRETS_KEY or JWT_SECRET fallback.
  Existing plaintext secrets encrypt on boot; deploy/exec paths decrypt
  transparently. Masked-echo writes preserve stored ciphertext.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/backend/internal/secrets/secrets.go

@@ -0,0 +1,98 @@
+package secrets
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/base64"
+	"fmt"
+	"log"
+	"strings"
+	"sync"
+)
+
+// Prefix marks AES-GCM-encrypted values in environment_variables.value.
+// Plaintext rows keep working — Decrypt returns them unchanged, so the
+// rollout is transparent encrypt-on-write / decrypt-on-read.
+const Prefix = "enc:v1:"
+
+var (
+	keyOnce sync.Once
+	key     []byte
+	enabled bool
+)
+
+// Configure derives the AES-256 key. SECRETS_KEY wins; JWT_SECRET is the
+// fallback so existing installs need no new config. With neither, encrypt
+// degrades to plaintext with a single warning.
+func Configure(secretsKey, jwtSecret string) {
+	keyOnce.Do(func() {
+		seed := secretsKey
+		if seed == "" {
+			seed = jwtSecret
+		}
+		if seed == "" {
+			log.Printf("secrets: no SECRETS_KEY or JWT_SECRET — secret variables stay plaintext")
+			return
+		}
+		sum := sha256.Sum256([]byte("containr-env-secrets:" + seed))
+		key = sum[:]
+		enabled = true
+	})
+}
+
+func IsEncrypted(value string) bool {
+	return strings.HasPrefix(value, Prefix)
+}
+
+// Encrypt returns value unchanged if disabled or already encrypted.
+func Encrypt(value string) string {
+	if !enabled || IsEncrypted(value) {
+		return value
+	}
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return value
+	}
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return value
+	}
+	nonce := make([]byte, gcm.NonceSize())
+	if _, err := rand.Read(nonce); err != nil {
+		return value
+	}
+	sealed := gcm.Seal(nonce, nonce, []byte(value), nil)
+	return Prefix + base64.StdEncoding.EncodeToString(sealed)
+}
+
+// Decrypt returns plaintext for enc:v1 values, the input otherwise.
+// Corrupt ciphertext fails soft to the stored value rather than erroring
+// the deploy path — an unreadable secret is no worse than a plaintext one.
+func Decrypt(value string) string {
+	if !enabled || !IsEncrypted(value) {
+		return value
+	}
+	raw, err := base64.StdEncoding.DecodeString(strings.TrimPrefix(value, Prefix))
+	if err != nil {
+		return value
+	}
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return value
+	}
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return value
+	}
+	if len(raw) < gcm.NonceSize() {
+		return value
+	}
+	plain, err := gcm.Open(nil, raw[:gcm.NonceSize()], raw[gcm.NonceSize():], nil)
+	if err != nil {
+		log.Printf("secrets: decrypt failed (%v) — check SECRETS_KEY/JWT_SECRET rotation", fmt.Errorf("%w", err))
+		return value
+	}
+	return string(plain)
+}