fix(security): phase 1 critical fixes for public release

- Redact PostgreSQL DSN password from stdout/logs
- Harden .dockerignore to exclude .ssh/, .claude/, *.db, *.local files
- SSRF protection: block private/loopback/link-local IPs by default
  (UPTOP_ALLOW_PRIVATE_TARGETS=true to override for homelab use)
- Fix email header injection via CRLF in monitor names
- AES-256-GCM encryption for alert credentials at rest
  (UPTOP_ENCRYPTION_KEY env var, migrate-secrets subcommand)
- TLS support for HTTP server (UPTOP_TLS_CERT/UPTOP_TLS_KEY)
  with HSTS header when TLS enabled

internal/store/crypto.go

@@ -0,0 +1,70 @@
+package store
+
+import (
+	"crypto/aes"
+	"crypto/cipher"
+	"crypto/rand"
+	"encoding/base64"
+	"encoding/hex"
+	"fmt"
+	"io"
+	"strings"
+)
+
+const encryptedPrefix = "enc:"
+
+type Encryptor struct {
+	gcm cipher.AEAD
+}
+
+func NewEncryptor(hexKey string) (*Encryptor, error) {
+	key, err := hex.DecodeString(hexKey)
+	if err != nil {
+		return nil, fmt.Errorf("invalid encryption key: must be hex-encoded: %w", err)
+	}
+	if len(key) != 32 {
+		return nil, fmt.Errorf("invalid encryption key: must be 32 bytes (64 hex chars), got %d bytes", len(key))
+	}
+	block, err := aes.NewCipher(key)
+	if err != nil {
+		return nil, fmt.Errorf("create cipher: %w", err)
+	}
+	gcm, err := cipher.NewGCM(block)
+	if err != nil {
+		return nil, fmt.Errorf("create GCM: %w", err)
+	}
+	return &Encryptor{gcm: gcm}, nil
+}
+
+func (e *Encryptor) Encrypt(plaintext string) (string, error) {
+	nonce := make([]byte, e.gcm.NonceSize())
+	if _, err := io.ReadFull(rand.Reader, nonce); err != nil {
+		return "", fmt.Errorf("generate nonce: %w", err)
+	}
+	ciphertext := e.gcm.Seal(nonce, nonce, []byte(plaintext), nil)
+	return encryptedPrefix + base64.StdEncoding.EncodeToString(ciphertext), nil
+}
+
+func (e *Encryptor) Decrypt(data string) (string, error) {
+	if !strings.HasPrefix(data, encryptedPrefix) {
+		return data, nil
+	}
+	raw, err := base64.StdEncoding.DecodeString(strings.TrimPrefix(data, encryptedPrefix))
+	if err != nil {
+		return "", fmt.Errorf("decode base64: %w", err)
+	}
+	nonceSize := e.gcm.NonceSize()
+	if len(raw) < nonceSize {
+		return "", fmt.Errorf("ciphertext too short")
+	}
+	nonce, ciphertext := raw[:nonceSize], raw[nonceSize:]
+	plaintext, err := e.gcm.Open(nil, nonce, ciphertext, nil)
+	if err != nil {
+		return "", fmt.Errorf("decrypt: %w", err)
+	}
+	return string(plaintext), nil
+}
+
+func IsEncrypted(data string) bool {
+	return strings.HasPrefix(data, encryptedPrefix)
+}