Document theme picker, holiday catalog, and event/scope limitations

- Add Theme options (System/Light/Dark/KashCal Teal) to settings; replace
  stale note that claimed there was no in-app theme switch
- Add built-in holiday calendar catalog to ICS subscriptions
- Expand known limitations: events-only (no CardDAV/tasks), Google/Outlook
  via device calendars, seven built-in views, and servers that accept but
  don't deliver invitations

Author: one-kash

docs/features/settings.md

@@ -19,15 +19,19 @@ Open the navigation drawer (swipe from the left edge, or tap the menu icon) and
 
 ## Appearance
 
+- **Theme:** choose how KashCal looks:
+  - **System default** follows your phone's light or dark setting and switches automatically when your phone does.
+  - **Light** and **Dark** pin the app to that appearance regardless of the system setting.
+  - **KashCal Teal** applies the app's teal palette, still following your phone's light or dark setting.
 - **Event Emojis:** when on, KashCal shows an emoji next to an event based on its title (a cake for a birthday, a plane for a flight). Turn it off for a plainer list.
 - **Time Format:** 12-hour, 24-hour, or follow the system. The row shows a live example of the current format.
 - **Start Week On:** whether your week begins on the system default, Monday, Sunday, or Saturday. This changes every calendar grid at once.
 - **Week Numbers:** show the ISO week number alongside the month grid.
 - **Show declined events:** keep events you've declined visible, shown dimmed with a strikethrough, instead of hiding them.
 - **Widget Event Limit:** how many events each day shows in the home-screen widgets. The default is 5.
 
-:::note[Light and dark mode]
-KashCal follows your **system** light/dark setting, so it switches automatically when your phone does. There's no separate in-app theme switch. On Android 12 and newer it also picks up your **Material You** wallpaper colors.
+:::note[Material You colors]
+With the **System default**, **Light**, and **Dark** themes, KashCal picks up your **Material You** wallpaper colors on Android 12 and newer. **KashCal Teal** uses its own fixed palette instead.
 :::
 
 ## Creating events

docs/help/known-limitations.md

@@ -19,8 +19,12 @@ support scheduling:
 - **Some accounts don't support inviting people at all**, in which case KashCal tells
   you:
   > Inviting people isn't available on this account
-- A few servers have their own quirks around how invitations are delivered. Major
-  services generally work well.
+- **A few servers accept guests but never deliver the invitation.** Some CalDAV
+  servers (SOGo and mailbox.org are the ones we've seen) save your guests without
+  sending anyone an email, and they don't report this back, so KashCal can't warn you
+  in advance. The guests are on the event, but they aren't notified. This matches how
+  other calendar apps behave: when a server won't deliver, sending the invite is up to
+  you. Major services like iCloud generally deliver as expected.
 
 ## RSVP to a recurring event covers the whole series
 
@@ -47,6 +51,38 @@ refresh any time for an immediate sync.
 Events from an [ICS subscription](../sync/ics-subscriptions.md) can't be edited in
 KashCal. They belong to the source feed.
 
+## KashCal handles calendar events, not contacts or tasks
+
+KashCal is an events app. It reads and writes calendar events (the `VEVENT` part of
+the calendar standard) and nothing else:
+
+- **No contacts (CardDAV).** KashCal doesn't sync address books. It does read
+  birthdays and anniversaries from your phone's contacts, see
+  [Contact birthdays](../features/birthdays.md), but that's a one-way read, not
+  CardDAV.
+- **No tasks or to-dos (VTODO), journals, or attachments.** Calendars that contain
+  only tasks or journal entries are skipped during sync rather than shown as empty.
+
+This keeps the app focused and fast. A separate tasks or contacts app is the right
+tool for those.
+
+## Google and Outlook connect through your phone, not directly
+
+KashCal talks to iCloud and CalDAV servers directly, but neither Google nor Microsoft
+offers that kind of access anymore. Google removed third-party CalDAV access, and
+Outlook and Microsoft 365 don't expose CalDAV at all. So both come in through the
+**Device calendars** bridge instead: if the Google or Outlook app already syncs those
+calendars to your phone, KashCal can show and edit them. See
+[Device calendars](../sync/device-calendars.md) and the
+[FAQ](./faq.md#does-it-work-with-google-calendar-or-outlook).
+
+## Views are the seven built in
+
+KashCal offers month, agenda, day, 3-day, week, full-month, and year views, plus
+Insights. There's no multi-month grid (like a 3- or 6-month view) and no
+non-Gregorian calendar system (such as Hijri or lunar). The Gregorian calendar is the
+only one available.
+
 ---
 
 If something you expected to work isn't listed here and isn't covered in

docs/sync/ics-subscriptions.md

@@ -13,7 +13,30 @@ Follow the calendars someone else keeps up to date: public holidays, your team's
 fixtures, school terms, release dates, and more. These are free, read-only ICS
 links, not paid subscriptions.
 
-## Add a feed
+## Add a holiday calendar
+
+The quickest way to get started is the built-in holiday catalog, so you don't have to
+hunt for a URL:
+
+1. Open **Settings** → **Calendar Feeds**.
+2. Tap **Add holiday calendar**.
+3. Search for your country and tap it to subscribe.
+
+KashCal ships a catalog of national holiday calendars for many countries (some in
+more than one language). Countries you're already subscribed to are marked **Added**.
+Each one is a regular calendar feed, so it stays up to date on its own and follows all
+the behavior below.
+
+:::note[Where these come from]
+The holiday calendars come from Mozilla Thunderbird's public holiday feeds, licensed
+under CC BY-SA 3.0. KashCal only points at those feeds; it doesn't host the calendar
+data itself.
+:::
+
+## Add any other feed
+
+For a feed that isn't in the holiday catalog (a sports schedule, your school's term
+dates, and so on):
 
 1. Open **Settings** → **Calendar Feeds** → add a calendar.
 2. Paste the feed's URL. It must start with `http://`, `https://`, or `webcal://`: