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/alert/alert_test.go

@@ -3,10 +3,11 @@ package alert
 import (
 	"context"
 	"encoding/json"
-	"gitea.lerkolabs.com/lerko/uptop/internal/models"
 	"net/http"
 	"net/http/httptest"
 	"testing"
+
+	"gitea.lerkolabs.com/lerko/uptop/internal/models"
 )
 
 func TestHTTPProviderDiscord(t *testing.T) {
@@ -212,3 +213,20 @@ func TestGetProviderUnknown(t *testing.T) {
 		t.Error("expected nil for unknown provider type")
 	}
 }
+
+func TestSanitizeHeader(t *testing.T) {
+	tests := []struct {
+		input, want string
+	}{
+		{"normal subject", "normal subject"},
+		{"inject\r\nBcc: evil@bad.com", "injectBcc: evil@bad.com"},
+		{"has\nnewline", "hasnewline"},
+		{"has\rcarriage", "hascarriage"},
+	}
+	for _, tt := range tests {
+		got := sanitizeHeader(tt.input)
+		if got != tt.want {
+			t.Errorf("sanitizeHeader(%q) = %q, want %q", tt.input, got, tt.want)
+		}
+	}
+}