feat: Phase 6 — require_active_service decorator + wizard install wiring

Email/calendar/files routes now return 404 when the service is not
installed, using a require_active_service decorator that checks
ServiceRegistry. Status endpoints are exempt so health checks always work.

SetupManager.complete_setup() now accepts a service_store_manager and
installs any wizard-selected services in a background daemon thread after
setup completes. Failures are logged but do not fail the wizard.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

api/routes/email.py

@@ -1,9 +1,12 @@
 import logging
 from flask import Blueprint, request, jsonify
+from routes import require_active_service
+
 logger = logging.getLogger('picell')
 bp = Blueprint('email', __name__)
 
 @bp.route('/api/email/users', methods=['GET'])
+@require_active_service('email')
 def get_email_users():
     """Get email users."""
     try:
@@ -15,6 +18,7 @@ def get_email_users():
         return jsonify({"error": str(e)}), 500
 
 @bp.route('/api/email/users', methods=['POST'])
+@require_active_service('email')
 def create_email_user():
     """Create email user."""
     try:
@@ -34,6 +38,7 @@ def create_email_user():
         return jsonify({"error": str(e)}), 500
 
 @bp.route('/api/email/users/<username>', methods=['DELETE'])
+@require_active_service('email')
 def delete_email_user(username):
     """Delete email user."""
     try:
@@ -57,6 +62,7 @@ def get_email_status():
         return jsonify({"error": str(e)}), 500
 
 @bp.route('/api/email/connectivity', methods=['GET'])
+@require_active_service('email')
 def test_email_connectivity():
     """Test email connectivity."""
     try:
@@ -68,6 +74,7 @@ def test_email_connectivity():
         return jsonify({"error": str(e)}), 500
 
 @bp.route('/api/email/send', methods=['POST'])
+@require_active_service('email')
 def send_email():
     try:
         from app import email_manager
@@ -81,6 +88,7 @@ def send_email():
         return jsonify({"error": str(e)}), 500
 
 @bp.route('/api/email/mailbox/<username>', methods=['GET'])
+@require_active_service('email')
 def get_mailbox_info(username):
     """Get mailbox information."""
     try: