fix(browse): replace SingleFile with direct Go HTTP fetch; fix ranking schema and cache-hit ranking gap

- Remove SingleFile CLI and Node.js from Dockerfile; runtime base reverted to alpine:3.21
- Replace triggerBrowseSnapshot with triggerDirectScrape: plain Go HTTP GET to novelfire.net
  (page is server-rendered, no browser needed)
- Fix Accept-Encoding bug: stop setting header manually so Go transport auto-decompresses gzip
- Add in-memory browse cache fallback (browseMemCache) for when MinIO and upstream both fail
- Add warmBrowseCache() startup goroutine
- Call triggerDirectScrape on MinIO cache hits too, so PocketBase ranking records are
  repopulated after a schema reset or fresh deploy without waiting for a cache miss
- Fix grid view cards: wrap in <a> instead of <div> so clicking navigates to book detail
- Remove SINGLEFILE_PATH and BROWSERLESS_URL env vars from Dockerfile

ui/src/routes/browse/+page.svelte

@@ -250,7 +250,10 @@
 	<!-- ── Grid view ─────────────────────────────────────────────────────── -->
 	<div class="grid grid-cols-2 sm:grid-cols-3 md:grid-cols-4 lg:grid-cols-5 xl:grid-cols-6 gap-4">
 		{#each data.novels as novel}
-			<div class="group flex flex-col rounded-lg overflow-hidden bg-zinc-800 border border-zinc-700 hover:border-zinc-500 transition-colors relative">
+			<a
+				href="/books/{novel.slug}"
+				class="group flex flex-col rounded-lg overflow-hidden bg-zinc-800 border border-zinc-700 hover:border-zinc-500 transition-colors relative"
+			>
 				<!-- Cover -->
 				<div class="aspect-[2/3] bg-zinc-900 overflow-hidden relative">
 					{#if novel.cover}
@@ -302,7 +305,7 @@
 								<span class="text-xs text-red-400 font-medium">Error</span>
 							{:else}
 								<button
-									onclick={() => scrapeNovel(novel)}
+									onclick={(e) => { e.preventDefault(); scrapeNovel(novel); }}
 									disabled={scraping[novel.slug]}
 									class="w-full text-xs px-2 py-1 rounded bg-amber-500/20 text-amber-300 hover:bg-amber-500/40 transition-colors disabled:opacity-50 disabled:cursor-not-allowed border border-amber-500/30"
 								>
@@ -312,7 +315,7 @@
 						</div>
 					{/if}
 				</div>
-			</div>
+			</a>
 		{/each}
 	</div>