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_test.go

@@ -11,7 +11,7 @@ import (
 	"testing"
 	"time"
 
-	"mangabm/backend/internal/store"
+	"bookmarkmanager/backend/internal/store"
 )
 
 func TestLoadLatestPollDefaults(t *testing.T) {
@@ -243,3 +243,76 @@ func TestGzipCompressesTextNotFonts(t *testing.T) {
 		t.Errorf("Content-Encoding without Accept-Encoding = %q, want empty", enc)
 	}
 }
+
+func TestPutKindValidation(t *testing.T) {
+	cases := []struct {
+		name string
+		kind string
+		want int
+	}{
+		{"empty is no opinion", "", http.StatusOK},
+		{"manga", "manga", http.StatusOK},
+		{"novel", "novel", http.StatusOK},
+		{"garbage", "comic", http.StatusBadRequest},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			srv := newTestServer(t)
+			body := fmt.Sprintf(`{"title":"Solo","kind":%q}`, tc.kind)
+			req := auth(httptest.NewRequest(http.MethodPut, "/bookmarks/asura:solo",
+				strings.NewReader(body)))
+			rr := httptest.NewRecorder()
+			srv.ServeHTTP(rr, req)
+
+			if rr.Code != tc.want {
+				t.Fatalf("status = %d, want %d (body %s)", rr.Code, tc.want, rr.Body.String())
+			}
+			if tc.want != http.StatusOK {
+				return
+			}
+			var got store.Bookmark
+			if err := json.Unmarshal(rr.Body.Bytes(), &got); err != nil {
+				t.Fatalf("decode: %v", err)
+			}
+			want := tc.kind
+			if want == "" {
+				want = "manga"
+			}
+			if got.Kind != want {
+				t.Fatalf("stored kind = %q, want %q", got.Kind, want)
+			}
+		})
+	}
+}
+
+// The preserve path: a novel row re-PUT by a client that omits the field
+// entirely must stay a novel and still record the progress it carried.
+func TestPutOmittedKindPreservesNovelAndAppliesProgress(t *testing.T) {
+	srv := newTestServer(t)
+	const key = "/bookmarks/lightnovelworld:a-will-eternal"
+
+	seed := auth(httptest.NewRequest(http.MethodPut, key,
+		strings.NewReader(`{"title":"A Will Eternal","kind":"novel","last_chapter_num":10}`)))
+	rr := httptest.NewRecorder()
+	srv.ServeHTTP(rr, seed)
+	if rr.Code != http.StatusOK {
+		t.Fatalf("seed status = %d, want 200 (%s)", rr.Code, rr.Body.String())
+	}
+
+	rr = httptest.NewRecorder()
+	srv.ServeHTTP(rr, auth(httptest.NewRequest(http.MethodPut, key,
+		strings.NewReader(`{"title":"A Will Eternal","last_chapter_num":11}`))))
+	if rr.Code != http.StatusOK {
+		t.Fatalf("status = %d, want 200 (%s)", rr.Code, rr.Body.String())
+	}
+	var got store.Bookmark
+	if err := json.Unmarshal(rr.Body.Bytes(), &got); err != nil {
+		t.Fatalf("decode: %v", err)
+	}
+	if got.Kind != store.KindNovel {
+		t.Fatalf("Kind = %q, want novel", got.Kind)
+	}
+	if got.LastChapterNum != 11 {
+		t.Fatalf("LastChapterNum = %v, want 11", got.LastChapterNum)
+	}
+}