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/index.html

@@ -15,13 +15,6 @@
             <h1 class="title">YellowJacket</h1>
             <h3 class="subtitle">Music how it was meant to bee.</h3>
         </hgroup>
-        <div id="library-only-toggle" class="mode-toggle" title="Toggle Library Only mode">
-            <wa-icon name="globe" class="mode-icon mode-icon-globe"></wa-icon>
-            <div class="mode-toggle-track">
-                <div class="mode-toggle-thumb"></div>
-            </div>
-            <wa-icon name="hard-drive" class="mode-icon mode-icon-local"></wa-icon>
-        </div>
         <library-filter></library-filter>
         <search-bar></search-bar>
         <job-indicator></job-indicator>