feat: data lifecycle rewrite, download clients, wanted list, and central catalog index

Ships the fresh-start schema cleanup: rebuilt explore catalog index
pipeline (dump import, artifact fetch/build, incremental listen-count
refresh), a new download subsystem (Lidarr/Prowlarr/qBittorrent/SABnzbd/
slskd/yt-dlp providers, staging, reconciliation, wanted list), and the
supporting schema/query/store changes across backend and frontend.

Also includes two smaller follow-ups: bump the central index's
rebuild-after cadence from 90 to 180 days, and remove the Explore
"library only" online/offline toggle entirely (frontend-only, no
backend counterpart) rather than carry unused UI/state.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Y2Agd9af5hE7qzti2ackiS

frontend/wailsjs/go/explore/Service.js

@@ -30,6 +30,10 @@ export function CheckLibraryMBIDs(arg1) {
   return window['go']['explore']['Service']['CheckLibraryMBIDs'](arg1);
 }
 
+export function CoreCatalogImported() {
+  return window['go']['explore']['Service']['CoreCatalogImported']();
+}
+
 export function CoverArtGroupURL(arg1) {
   return window['go']['explore']['Service']['CoverArtGroupURL'](arg1);
 }
@@ -98,6 +102,18 @@ export function GetTrackThumbnails(arg1) {
   return window['go']['explore']['Service']['GetTrackThumbnails'](arg1);
 }
 
+export function IndexBaselineSeries() {
+  return window['go']['explore']['Service']['IndexBaselineSeries']();
+}
+
+export function IndexImportComplete() {
+  return window['go']['explore']['Service']['IndexImportComplete']();
+}
+
+export function IndexLastImported() {
+  return window['go']['explore']['Service']['IndexLastImported']();
+}
+
 export function InvalidateIndexDiscographies() {
   return window['go']['explore']['Service']['InvalidateIndexDiscographies']();
 }
@@ -134,6 +150,10 @@ export function PrefetchReleases(arg1) {
   return window['go']['explore']['Service']['PrefetchReleases'](arg1);
 }
 
+export function PrepareIndexRebuild() {
+  return window['go']['explore']['Service']['PrepareIndexRebuild']();
+}
+
 export function RebuildLyricsIndex() {
   return window['go']['explore']['Service']['RebuildLyricsIndex']();
 }
@@ -146,6 +166,10 @@ export function RecordSearchClick(arg1, arg2, arg3) {
   return window['go']['explore']['Service']['RecordSearchClick'](arg1, arg2, arg3);
 }
 
+export function RefreshIndexNow(arg1) {
+  return window['go']['explore']['Service']['RefreshIndexNow'](arg1);
+}
+
 export function RefreshListenCounts() {
   return window['go']['explore']['Service']['RefreshListenCounts']();
 }