fix(email): validate IMAP/SMTP ports instead of crashing with 500 (#4464)

The email-account endpoints coerced user-supplied ports with a bare int(data.get("imap_port") or 993), so a non-numeric port (e.g. "imap") raised ValueError and surfaced as an HTTP 500 in the create, update, and test-config endpoints.

Add a _coerce_port(value, default) -> (port, error) helper and use it in all three endpoints, returning the endpoints standard {"ok": False, "error": ...} response (matching the existing "name required" validation) instead of crashing. A blank or missing port still falls back to the default (993/465).

tests/test_email_account_port_validation.py

@@ -0,0 +1,56 @@
+"""User-supplied IMAP/SMTP ports must not crash the email-account endpoints.
+
+A non-numeric port (for example ``"imap"`` or ``"993x"``) previously reached an
+unguarded ``int(...)`` in create / update / test-config and raised ``ValueError``,
+which surfaces as an HTTP 500. The endpoints should reject it with their standard
+``{"ok": False, "error": ...}`` response instead.
+"""
+
+import pytest
+
+
+def _route_endpoint(router, path: str, method: str):
+    method = method.upper()
+    for route in router.routes:
+        if route.path == path and method in getattr(route, "methods", set()):
+            return route.endpoint
+    raise AssertionError(f"route not found: {method} {path}")
+
+
+def test_coerce_port_accepts_int_and_numeric_string():
+    import routes.email_routes as email_routes
+    assert email_routes._coerce_port(2525, 993) == (2525, None)
+    assert email_routes._coerce_port("465", 993) == (465, None)
+
+
+def test_coerce_port_blank_uses_default():
+    import routes.email_routes as email_routes
+    assert email_routes._coerce_port(None, 993) == (993, None)
+    assert email_routes._coerce_port("", 465) == (465, None)
+
+
+def test_coerce_port_rejects_non_numeric():
+    import routes.email_routes as email_routes
+    port, err = email_routes._coerce_port("imap", 993)
+    assert port is None
+    assert err and "port" in err.lower()
+
+
+@pytest.mark.asyncio
+async def test_create_account_rejects_non_numeric_port():
+    """A bad port is rejected before any DB work, with the endpoint's error shape."""
+    import routes.email_routes as email_routes
+    router = email_routes.setup_email_routes()
+    create = _route_endpoint(router, "/api/email/accounts", "POST")
+    result = await create(
+        {
+            "name": "Test",
+            "imap_host": "mail.example.com",
+            "imap_user": "u",
+            "imap_password": "p",
+            "imap_port": "not-a-number",
+        },
+        owner="alice",
+    )
+    assert result["ok"] is False
+    assert "port" in result["error"].lower()