Add a Readarr mock instance to the demo

Adds darkalex17/readarr-mock, built from ghcr.io/pennydreadful/bookshelf:softcover
(the maintained Readarr continuation; the LinuxServer image is discontinued and
its metadata endpoint no longer resolves). The captured config carries 6 authors,
327 books, 39 book files, 4 tags, 7 indexers, 193 history rows and one root
folder at /books, with minimal EPUBs under mock-htpc/books so the files show as
imported.

Prowlarr now registers Readarr as a synced application, so its config is
recaptured and the prowlarr-mock image must be rebuilt and pushed alongside.

The compose file, managarr config, justfile recipes and README gain the fourth
instance. The demo script needs no change; it fetches the compose file and
config from main at run time.

Requires a Managarr release with Readarr support, since the demo script runs
the published darkalex17/managarr image against these files.

mock-htpc/prowlarr/Definitions/retrotoon.yml

@@ -0,0 +1,109 @@
+---
+id: retrotoon
+name: RetroToon
+description: "RetroToon is a Private Torrent Tracker for ANIMATED MOVIES / TV"
+language: en-US
+type: private
+encoding: UTF-8
+links:
+  - https://www.retrotoon.world/
+
+caps:
+  categorymappings:
+    # from https://www.retrotoon.world/torznab.php?t=caps
+    - {id: 2000, cat: Movies, desc: "Movies"}
+    - {id: 3000, cat: Audio, desc: "Audio"}
+    - {id: 3030, cat: Audio, desc: "Soundtrack"}
+    - {id: 5000, cat: TV, desc: "TV"}
+    - {id: 5070, cat: TV/Anime, desc: "TV/Anime"}
+    - {id: 5080, cat: TV/Documentary, desc: "TV/Documentary"}
+    - {id: 7000, cat: Books, desc: "Books"}
+    - {id: 7030, cat: Books/Comics, desc: "Comics"}
+    - {id: 8000, cat: TV/Anime, desc: "Adult Animation"}
+    - {id: 100008, cat: TV/Anime, desc: "Adult Animation"}
+
+  modes:
+    search: [q]
+    tv-search: [q, season, ep]
+    movie-search: [q]
+    book-search: [q]
+    music-search: [q]
+
+settings:
+  - name: apikey
+    type: text
+    label: API Key
+  - name: info_key
+    type: info
+    label: About your API Key
+    default: "You can find your API Key by accessing the <a href=\"https://www.retrotoon.world/prowlarr.php\" target=\"_blank\">RetroToon Prowlarr & Torznab integration</a> page and scrolling down to the <b>Your Passkey</b> section. (Passkey is the same as the APIkey)."
+
+login:
+  # returns "401 Unauthorized, check your credentials" if apikey is invalid
+  path: torznab.php
+  method: get
+  inputs:
+    apikey: "{{ .Config.apikey }}"
+    t: search
+    limit: 1
+
+search:
+  paths:
+    - path: torznab.php
+      response:
+        type: xml
+
+  inputs:
+    apikey: "{{ .Config.apikey }}"
+    t: "{{ .Query.Type }}"
+    q: "{{ .Keywords }}"
+    cat: "{{ join .Categories \",\" }}"
+    season: "{{ .Query.Season }}"
+    ep: "{{ .Query.Ep }}"
+    limit: 100
+
+  rows:
+    selector: rss > channel > item
+
+  fields:
+    category:
+      selector: "[name=category]"
+      attribute: value
+    title:
+      selector: title
+    details:
+      selector: link
+    download:
+      selector: enclosure
+      attribute: url
+    date:
+      # Thu, 15 Jan 2026 16:24:34 +0000
+      selector: pubDate
+      filters:
+        - name: dateparse
+          args: "ddd, dd MMM yyyy HH:mm:ss zzz"
+    size:
+      selector: "[name=size]"
+      attribute: value
+    imdbid:
+      selector: "[name=imdbid]"
+      attribute: value
+    seeders:
+      selector: "[name=seeders]"
+      attribute: value
+    leechers:
+      selector: "[name=leechers]"
+      attribute: value
+    grabs:
+      selector: "[name=grabs]"
+      attribute: value
+    downloadvolumefactor:
+      selector: "[name=downloadvolumefactor]"
+      attribute: value
+    uploadvolumefactor:
+      selector: "[name=uploadvolumefactor]"
+      attribute: value
+    minimumseedtime:
+      # 3 days (as seconds = 3 x 24 x 60 x 60)
+      text: 259200
+# torznab xml