rebrand: MangaBM → BookmarkManager, add novel library support (#15)

Two intertwined changes — the rebrand and the novel library were developed on
the same branch because the novel UI plumbing is part of the new "Bookmark
Manager" wordmark in the web shell.

## What it does

- **Rebrand**: MangaBM → BookmarkManager across the Go module, compose stack,
  env vars, Traefik hostnames, container/image names, userscript storage
  prefixes (`mangabm:cache` → `bmgr:manga:cache`, `mangabm:queue` → `bmgr:manga:queue`),
  and docs.
- **Novel library**: same backend, two libraries. New `kind` column splits
  bookmarks into `manga` / `novel`; PUT validates it. Two userscripts:
  - `manga-bookmark.user.js` — unchanged behaviour, just stamps its own `kind`.
  - `novel-bookmark.user.js` — separate Violentmonkey install with adapters
    for **novelfull.com** (polled via headless browser — Cloudflare JS
    challenge) and **lightnovelworld.net** (polled via plain TLS).
- **Web UI**: library switch on the app shell. Login art, libswitch, and
  novel-site colours from the Cinder design snapshot.

## Plumbing

- `addedColumns` ALTER for `kind` runs on first start after upgrade; every
  pre-existing row is backfilled to `'manga'`. No manual SQL, no down-time.
- `ALLOWED_ORIGINS` gains the two novel sites.
- New `NOVEL_USERSCRIPT_PATH` env (default `/userscript/novel-bookmark.user.js`),
  bindmounted alongside the manga script.
- Traefik router names `mangabm*` → `bmapi*` / `bmweb*`.

## Test status

- `go test ./...` — green
- `node --test userscript/test/logic.test.js` — 34 pass
- `node --test userscript/test/novel-logic.test.js` — 11 pass
- `node --check` on both userscripts — clean

## Notes for the redeploy

.env keys were renamed (`MANGA_API_HOST` → `BOOKMARK_API_HOST`,
`MANGA_WEB_HOST` → `BOOKMARK_WEB_HOST`). Update DNS / Traefik labels on the
prod override before pulling, otherwise the public hostnames go dark.
See the redeploy instructions I'll post next to this PR.

Reviewed-on: #15
Co-authored-by: Sulthan Zaki <sultankiki05@gmail.com>
Co-committed-by: Sulthan Zaki <sultankiki05@gmail.com>

backend/AGENTS.md

@@ -0,0 +1,82 @@
+Guidance for OpenCode (and Claude Code) working under `backend/`. See root `AGENTS.md` for the project-wide architecture diagram, hard constraints, and design system.
+
+- **Backend** (`backend/`): stdlib `net/http` (handful routes, no framework) + `modernc.org/sqlite` (pure Go, `CGO_ENABLED=0` -> static binary -> distroless/scratch image). Reverse proxy terminates TLS; Go service listens plain `:8080`.
+  Single binary, split into packages under `backend/internal/`: `store`
+  (Bookmark type, SQLite persistence, migrations), `latest` (background
+  poller, site parsers, TLS fetcher), `session` (cookie signing, login
+  rate limiter), `httpmw` (Auth/Gzip/CORS middleware), `api` (JSON
+  bookmark handlers), `userscript` (userscript-serving handler), `web`
+  (browser UI handler + `templates/` + `static/`, `go:embed`-ed).
+  `backend/main.go` is the composition root — the only place that wires
+  packages together into `newRouter`. Root-level `*_test.go` hold
+  integration tests that exercise the full router; unit tests for a
+  package live beside it under `internal/`.
+- **Single-user store.** One `bookmarks` table keyed `<site>:<series_id>` (`asura`|`demonic`|`comix`|`kagane`). Sync **last-write-wins**. Schema and endpoint list in plan.
+- **Endpoints:** `GET /bookmarks`, `PUT /bookmarks/{key}` (upsert; see `updated_at` rule below), `DELETE /bookmarks/{key}`, `GET /healthz` (no auth).
+- **Web UI:** same binary serve password-gated browser UI on second
+  hostname — `GET /` (list, or login page when no session),
+  `POST /login`, `POST /logout`, `GET /static/*`, htmx fragment endpoints
+  under `/ui/*`. Templates + assets `go:embed`-ed under
+  `backend/internal/web/`, so `backend/Dockerfile` must copy the whole
+  `internal/` tree, not just `*.go`. Sessions stateless
+  HMAC cookies keyed off `API_TOKEN`; `WEB_PASSWORD` gates them, and when empty,
+  web routes not registered at all. UI mutations read-modify-write
+  through `Store.Get` + `Store.Upsert` so `updated_at` rule stays one
+  place. See `docs/superpowers/specs/2026-07-25-web-ui-design.md`.
+  **Design-tool caveat:** templates link `/static/style.css` root-absolutely
+  (correct — served from `/`), but impeccable detector resolves
+  stylesheet href with `path.resolve(fileDir, href)`, drops directory
+  on leading `/` and silently skip file. Relative href don't help
+  either: template's directory isn't its served path. So
+  `detect.mjs backend/internal/web/templates` reports **false clean** —
+  always pass `backend/internal/web/static` too. One finding there,
+  `overused-font` on "Instrument Serif", deliberate identity choice, not debt.
+- **Every action that moves series out of list is confirm-gated.**
+  Archive, finish, remove each open own `.confirm-row` disclosure
+  (`toggleConfirmRow(key, kind)` in `filter.js`, `kind` ∈
+  `archive|finish|remove`); restore fire instantly since it's the reversal.
+  Remove's row wear ember wash, two reversible ones wear `.calm` grey.
+  `--ember` stay reserved for new-chapter signal: busy bar and inline
+  error use `--mute`.
+- **Latest-chapter poller:** ticker goroutine in same binary re-check
+  each bookmarked series' newest published chapter from backend's own
+  network access, so `latest_chapter` stay fresh when user not
+  browsing. Second, parallel signal — userscript keep own
+  `maybeCaptureLatestOnSeriesPage`/`backgroundRefreshLatest` logic unchanged.
+  Two independent clocks: per-bookmark cooldown (`latest_checked_at` column,
+  enforced by `Store.DueForLatestCheck`'s WHERE clause) and wake interval.
+  Row stamped *before* fetch so broken series wait out full
+  cooldown instead of retrying every tick, and writes go through
+  `Store.Get` + `Store.Upsert` so new chapter never reorders list.
+  Fetches use `bogdanfinn/tls-client` with Chrome profile as defence in depth
+  against fingerprint-based blocking; any failure log and skip. kagane and
+  novelfull sit behind Cloudflare JavaScript challenges the TLS client can't
+  clear, so they are browser-only: fetched over CDP via `BROWSER_WS_URL`, and
+  simply not polled when that's unset. See
+  `docs/superpowers/specs/2026-07-26-server-latest-chapter-polling-design.md`.
+  Poller's `Store.Get` + `Store.Upsert` not wrapped in transaction, so
+  userscript `PUT` that commits between the two can get overwritten by
+  poller's stale re-read — reverting that read progress and, since stored
+  value now differs, moving `updated_at` and reordering list. Known,
+  accepted limitation for single-user deployment, not bug to fix.
+- **`updated_at` drives list order, so moves only on real reading progress:** server apply its timestamp when row new or `last_chapter_num` changes, else keep stored value — favouriting series or recording newly published chapter must not reorder list. `PUT` therefore returns row **as stored**, clients must adopt that response rather than own payload. See `plans/2026-07-25-bookmark-list-favorites-design.md` §4.
+- **Lifecycle buckets:** `status` on each bookmark is `reading` | `archived` |
+  `finished`, orthogonal to `favorite`. Archived and finished appear only in
+  own tab — not in All, Updated, Favourites, or recent strip. Poller keeps
+  checking archived series and skip finished ones. `finished` settable
+  only from web UI; `PUT /bookmarks/{key}` reject it with 400.
+  **Empty incoming status means "keep stored one"** — resolved on the
+  `VALUES` side of `Store.Upsert`, not conflict clause, since
+  `excluded.*` is post-evaluation row and default applied there would
+  wipe bucket on every PUT from client that predates column. See
+  `docs/superpowers/specs/2026-07-27-status-buckets-design.md`.
+- **Config via env:** `API_TOKEN`, `ALLOWED_ORIGINS` (comma list), `DB_PATH`
+  (default `/data/bookmarks.db`), `PORT` (default `8080`), `WEB_PASSWORD`
+  (gates browser UI; unset disable it),
+  `LATEST_CHAPTER_POLL_ENABLED`/`_COOLDOWN`/`_INTERVAL`/`_BATCH`/`_STAGGER`
+  (background latest-chapter poller; defaults on, `1h`/`10m`/`14`/`20s`).
+  `USERSCRIPT_PATH` (file served at `/u/{token}/manga-bookmark.user.js`,
+  default `/userscript/manga-bookmark.user.js`, supplied by bindmount).
+  `BROWSER_WS_URL` (headless-shell CDP endpoint for kagane and novelfull;
+  unset disables browser polling and leaves those sites to the userscript
+  alone).