Doc audit: fix all broken links + correct stale facts across the KB

Fanned out 5 read-only doc-auditor subagents (one per service group) that
fact-checked the knowledge base against the live system + repo config,
researched official setup docs online, and verified progress. Applied:
- All 34 broken links fixed (real pages / external URLs / correct relative
  paths); 0 broken links remain. No .AGENTTRASH links (the 4 mentions are
  accurate descriptive text, not links).
- Fact-check fixes: Readarr retired (May 2026), Radarr v4->v6, Calibre
  9.2.1 live, Calibre-Web 0.6.25 live, Copyparty v1.20.21, LLM index
  ncmoe 38 + 786432 ctx, frank-default-small active (not frank-pp-worker),
  Hermes/SearXNG/Grafana hostnames, Loki/Alloy local images, Observability
  diagram (Promtail->Alloy), VLLM retired note, DFlash status, benchmark
  live-drift notes, Homepage test count 116.

docs/Dankserver/readarr.md

@@ -1,5 +1,7 @@
 # Readarr
 
+> **RETIRED (May 2026).** The Servarr Team retired Readarr: its metadata became unusable and the community migration to Open Library stalled. There is no upstream development. Alternatives: the Bookshelf community fork, or the Calibre content server. See [Readarr (Retired)](https://wiki.servarr.com/readarr).
+
 Readarr manages ebooks and audiobooks in the *arr stack on Dankserver. It automatically searches, downloads, and organizes books into the Calibre library.
 
 **Host:** Dankserver — **Hostname:** `readarr.dankserver.local` — **Docs:** https://wiki.servarr.com/readarr