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/main.go

@@ -12,12 +12,12 @@ import (
 	"syscall"
 	"time"
 
-	"mangabm/backend/internal/api"
-	"mangabm/backend/internal/httpmw"
-	"mangabm/backend/internal/latest"
-	"mangabm/backend/internal/store"
-	"mangabm/backend/internal/userscript"
-	"mangabm/backend/internal/web"
+	"bookmarkmanager/backend/internal/api"
+	"bookmarkmanager/backend/internal/httpmw"
+	"bookmarkmanager/backend/internal/latest"
+	"bookmarkmanager/backend/internal/store"
+	"bookmarkmanager/backend/internal/userscript"
+	"bookmarkmanager/backend/internal/web"
 )
 
 // Config holds all runtime settings, sourced from environment variables.
@@ -31,6 +31,10 @@ type Config struct {
 	// UserscriptPath is the file served at /u/{token}/manga-bookmark.user.js.
 	// Supplied by a bindmount so the script can be edited without a rebuild.
 	UserscriptPath string
+	// NovelUserscriptPath is the file served at
+	// /u/{token}/novel-bookmark.user.js. Same bindmount, second script: the
+	// two libraries are separate installs.
+	NovelUserscriptPath string
 	// LatestPoll configures the background latest-chapter fetcher.
 	LatestPoll LatestPoll
 }
@@ -138,12 +142,13 @@ func loadLatestPoll() LatestPoll {
 
 func loadConfig() Config {
 	c := Config{
-		Token:          os.Getenv("API_TOKEN"),
-		DBPath:         envOr("DB_PATH", "/data/bookmarks.db"),
-		Port:           envOr("PORT", "8080"),
-		WebPassword:    os.Getenv("WEB_PASSWORD"),
-		UserscriptPath: envOr("USERSCRIPT_PATH", "/userscript/manga-bookmark.user.js"),
-		LatestPoll:     loadLatestPoll(),
+		Token:               os.Getenv("API_TOKEN"),
+		DBPath:              envOr("DB_PATH", "/data/bookmarks.db"),
+		Port:                envOr("PORT", "8080"),
+		WebPassword:         os.Getenv("WEB_PASSWORD"),
+		UserscriptPath:      envOr("USERSCRIPT_PATH", "/userscript/manga-bookmark.user.js"),
+		NovelUserscriptPath: envOr("NOVEL_USERSCRIPT_PATH", "/userscript/novel-bookmark.user.js"),
+		LatestPoll:          loadLatestPoll(),
 	}
 	for _, o := range strings.Split(os.Getenv("ALLOWED_ORIGINS"), ",") {
 		if o = strings.TrimSpace(o); o != "" {
@@ -164,6 +169,7 @@ func newRouter(s *store.Store, cfg Config) http.Handler {
 	// outside the WEB_PASSWORD gate (the script must be installable either
 	// way). The path segment carries the token instead.
 	mux.HandleFunc("GET /u/{token}/manga-bookmark.user.js", userscript.Handler(cfg.Token, cfg.UserscriptPath))
+	mux.HandleFunc("GET /u/{token}/novel-bookmark.user.js", userscript.Handler(cfg.Token, cfg.NovelUserscriptPath))
 
 	h := &api.Handler{Store: s}
 	protected := http.NewServeMux()