feat(rhema-code): add the colors setting with four palettes

The stored `colors` key names a palette — rhema (the default,
Jadeite), aquamarine, black-and-white, or dracula — and the
Appearance page of /settings cycles it live, like the theme and
icon toggles beside it. Each palette carries a dark and a light
appearance under the existing `theme` key; dracula's light side is
derived, the official palette ships only dark.

The appearance decision moves off token comparison: Theme now
answers is_dark() from the ground/text luminance, so palettes
beyond the original two get the right per-profile fallback tones.

integrations/rhema-calendar-integration/tests/ics.rs

@@ -0,0 +1,76 @@
+//! Offline integration tests: the ICS backend against an in-process
+//! wiremock server. Zero network.
+
+use rhema_calendar_integration::{Calendar, CalendarError, IcsCalendar, Window};
+use time::OffsetDateTime;
+use time::format_description::well_known::Rfc3339;
+use wiremock::matchers::{header, method, path};
+use wiremock::{Mock, MockServer, ResponseTemplate};
+
+const FEED_BODY: &str = "BEGIN:VCALENDAR\r\nVERSION:2.0\r\n\
+BEGIN:VEVENT\r\nUID:meet-1@x\r\nDTSTART:20261020T140000Z\r\nDTEND:20261020T150000Z\r\n\
+SUMMARY:kickoff\\, phase one\r\nLOCATION:paris\r\n\
+ORGANIZER:mailto:boss@example.net\r\nATTENDEE:mailto:alice@example.net\r\n\
+URL:https://meet.example.net/1\r\nEND:VEVENT\r\nEND:VCALENDAR\r\n";
+
+fn window() -> Window {
+    let from = OffsetDateTime::parse("2026-10-20T00:00:00Z", &Rfc3339).expect("parses");
+    Window::new(from, from + time::Duration::hours(24))
+}
+
+#[tokio::test]
+async fn a_poll_is_one_get_and_normalizes_the_feed() {
+    let server = MockServer::start().await;
+    Mock::given(method("GET"))
+        .and(path("/remote.php/dav/calendars/personal.ics"))
+        .respond_with(ResponseTemplate::new(200).set_body_string(FEED_BODY))
+        .mount(&server)
+        .await;
+
+    let feed = IcsCalendar::new(format!(
+        "{}/remote.php/dav/calendars/personal.ics",
+        server.uri()
+    ));
+    let events = feed.events(&window()).await.expect("polls");
+    assert_eq!(events.len(), 1);
+    let event = &events[0];
+    assert_eq!(event.title, "kickoff, phase one");
+    assert_eq!(event.location.as_deref(), Some("paris"));
+    assert_eq!(event.organizer.as_deref(), Some("boss@example.net"));
+    assert_eq!(event.attendees, vec!["alice@example.net".to_owned()]);
+    assert_eq!(event.url.as_deref(), Some("https://meet.example.net/1"));
+    assert_eq!(
+        event.start,
+        OffsetDateTime::parse("2026-10-20T14:00:00Z", &Rfc3339).expect("parses")
+    );
+}
+
+#[tokio::test]
+async fn a_token_rides_the_authorization_header_only() {
+    let server = MockServer::start().await;
+    Mock::given(method("GET"))
+        .and(header("Authorization", "Bearer sekrit"))
+        .respond_with(ResponseTemplate::new(200).set_body_string(FEED_BODY))
+        .mount(&server)
+        .await;
+
+    let feed = IcsCalendar::new(server.uri()).with_token("sekrit");
+    feed.events(&window()).await.expect("polls");
+}
+
+#[tokio::test]
+async fn a_server_error_is_named_with_a_bounded_body() {
+    let server = MockServer::start().await;
+    Mock::given(method("GET"))
+        .respond_with(ResponseTemplate::new(503).set_body_string("maintenance"))
+        .mount(&server)
+        .await;
+
+    let feed = IcsCalendar::new(server.uri());
+    let err = feed.events(&window()).await.expect_err("loud");
+    assert!(
+        matches!(err, CalendarError::Api { status: 503, .. }),
+        "got: {err:?}"
+    );
+    assert!(err.to_string().contains("maintenance"), "got: {err}");
+}