Moments: per-user saved pages and regions with one category (BL-0055)

Reader: bookmark button and M save the page (Flow: page at the reading
line, Book: the spread) with an optional dragged region, exactly one
category (Twist, Hot, Awesome, Cute, Funny, Feels) and a note. I now
toggles the bars; ? lists all keys. Keys dispatch through public/keys.js,
which also feeds the new Settings -> Keyboard shortcuts section.

Manga page: "Your moments" strip of crops (story or recent order,
category filters), viewer with step, full page, edit, delete and
"Open in reader" (read.html ...&p=). Moments point at pages by file
name and show "page moved" when the file is gone. Private per user.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -150,8 +150,9 @@ completeness.
   - In Flow: the bottom part of the screen goes forward, the top part goes back.
   - The middle of the page also toggles the controls (useful when a zoomed page fills the screen).
   - A horizontal swipe also turns pages on touch screens.
-  - Keys: arrows, Space / PageDown, `m` = controls, `f` = fullscreen.
-- **Controls stay out of the way:** they hide as soon as you turn a page or scroll, and come back only with a tap (middle of the page or beside it). Scrolling up never brings them back. The first time they hide, a short hint says so.
+  - Keys: arrows, Space / PageDown, `i` = controls, `m` = save a moment, `f` = fullscreen, `?` = all shortcuts (also under Settings → User → Keyboard shortcuts).
+- **Moments:** the bookmark button in the top bar (or `m`) saves the page you are on (in Book mode the spread) as a moment. Drag over the preview to keep only a region, and pick exactly one category: Twist, Hot, Awesome, Cute, Funny or Feels, plus an optional note. The button is filled on pages that already have one. Each manga page shows *Your moments* as a strip of crops, sorted by story or by when you saved them; click one to step through them, see the full page, edit, delete or jump into the reader at that page. Moments are private to each user.
+- **Controls stay out of the way:** they hide as soon as you turn a page or scroll, and come back only with a tap (middle of the page or beside it) or `i`. Scrolling up never brings them back. The first time they hide, a short hint says so.
 - **Controls:** the top bar has a chapter picker with every chapter of the manga, grouped by book, with ✓ for read ones. The bottom bar has the page slider, the mode switch, Shift, zoom, the version picker and previous/next chapter.
 - **Loading:** the next pages (next 3 in Page mode, next 2 spreads in Book mode) are downloaded and decoded in advance, so page turns don't flash. A page that still isn't there shows a spinner. On phones, "Add to home screen" opens the app without browser bars, and the ⛶ button (where supported) goes fullscreen.
 - **Progress** is saved per user and chapter version: the last page, whether the chapter is done, and book-mode shifts. The manga page offers *Continue*. Tap a chapter's status to mark it read/unread.