feat(01-01): create email blueprint with encrypted Tortoise ORM models

- Add EncryptedTextField for transparent Fernet encryption
- Create EmailAccount model with encrypted IMAP credentials
- Create EmailSyncStatus model for sync state tracking
- Create Email model with 30-day retention logic
- Follow existing blueprint patterns from users/conversation

blueprints/email/__init__.py

@@ -0,0 +1,16 @@
+"""
+Email blueprint for IMAP email ingestion.
+
+Provides API endpoints for managing email accounts and querying email content.
+Admin-only access enforced via lldap_admin group membership.
+"""
+
+from quart import Blueprint
+
+# Import models for Tortoise ORM registration
+from . import models  # noqa: F401
+
+# Create blueprint
+email_blueprint = Blueprint("email", __name__, url_prefix="/api/email")
+
+# Routes will be added in Phase 2