feat(browse): add SingleFile browse-page snapshot cache via MinIO

- New MinIO bucket 'libnovel-browse' (MINIO_BUCKET_BROWSE env) for storing
  self-contained HTML snapshots of novelfire browse pages
- Store interface gains SaveBrowsePage / GetBrowsePage / BrowsePageKey methods
- handleBrowse is now cache-first: serves from MinIO snapshot when available,
  then fires a background triggerBrowseSnapshot goroutine to populate cache
  on live-fetch (de-duplicated, 90s timeout)
- New 'save-browse' CLI subcommand to bulk-capture pages via SingleFile CLI
- Dockerfile: downloads pinned single-file-x86_64-linux binary (v2.0.83),
  adds gcompat + libstdc++ to Alpine runtime for glibc compatibility
- docker-compose: adds libnovel-browse bucket init and SINGLEFILE_PATH env
- .gitignore: exclude scraper/scraper build artifact

scraper/Dockerfile

@@ -12,15 +12,30 @@ COPY . .
 RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 \
     go build -ldflags="-s -w" -o /scraper ./cmd/scraper
 
+# ── single-file binary stage ───────────────────────────────────────────────────
+# Download the official pre-compiled single-file-cli binary (Deno-compiled,
+# statically linked for Linux x86_64 glibc).  We pin to a specific version so
+# image builds are reproducible; bump this ARG to upgrade.
+FROM alpine:3.20 AS singlefile-downloader
+ARG SINGLEFILE_VERSION=2.0.83
+RUN apk add --no-cache wget ca-certificates && \
+    wget -q -O /single-file \
+      "https://github.com/gildas-lormeau/single-file-cli/releases/download/v${SINGLEFILE_VERSION}/single-file-x86_64-linux" && \
+    chmod +x /single-file
+
 # ── Runtime stage ──────────────────────────────────────────────────────────────
 FROM alpine:3.20
 
-# ca-certificates is required for HTTPS requests to novelfire.net.
-RUN apk add --no-cache ca-certificates tzdata
+# ca-certificates: HTTPS to novelfire.net
+# gcompat: glibc compatibility shim so the glibc-linked single-file binary
+#          runs on musl/Alpine without needing a full glibc image.
+# libstdc++: required by the Deno runtime embedded in single-file
+RUN apk add --no-cache ca-certificates tzdata gcompat libstdc++
 
 WORKDIR /app
 
 COPY --from=builder /scraper /app/scraper
+COPY --from=singlefile-downloader /single-file /usr/local/bin/single-file
 
 # Create the default static output directory.
 RUN mkdir -p /app/static/books
@@ -36,6 +51,7 @@ ENV BROWSERLESS_STRATEGY=content
 ENV SCRAPER_WORKERS=0
 ENV SCRAPER_STATIC_ROOT=/app/static/books
 ENV SCRAPER_HTTP_ADDR=:8080
+ENV SINGLEFILE_PATH=/usr/local/bin/single-file
 
 EXPOSE 8080