Fix CI healthcheck endpoint and bundled install FK violations

Two bugs preventing the test-runners CI job from passing:

1. Health check used GET /api/v1/auth/login — a POST-only route that
   always returns 404. Changed to GET /api/v1/health which exists.

2. Bundled package install passed empty strings to FK-constrained
   columns (global_settings.updated_by, workflows.created_by),
   causing FOREIGN KEY constraint failures on every surface and
   workflow package. Fixed by resolving the bootstrap admin user ID
   at startup and threading it through the install path.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/handlers/packages.go

@@ -524,7 +524,7 @@ func (h *PackageHandler) InstallPackage(c *gin.Context) {
 					pkgPath := filepath.Join(h.bundledDir, libID+".pkg")
 					if _, statErr := os.Stat(pkgPath); statErr == nil {
 						log.Printf("[packages] auto-installing bundled dependency %s for %s", libID, pkgID)
-						if _, installErr := installBundledPackage(pkgPath, h.packagesDir, h.stores, h.runner); installErr != nil {
+						if _, installErr := installBundledPackage(pkgPath, h.packagesDir, h.stores, h.runner, c.GetString("user_id")); installErr != nil {
 							c.JSON(http.StatusBadRequest, gin.H{
 								"error": fmt.Sprintf("dependency %s auto-install failed: %v", libID, installErr),
 							})