stacks/miniflux: add r/comfyui, r/StableDiffusion, r/singularity to OPML

Subscribed live via Miniflux API; mirroring back to the canonical
OPML so a fresh deploy elsewhere starts with the same feed set.
All three land in the existing 'Subreddits — selfhosting' category
(retitled to mention image-gen + LLM + homelab to reflect scope).

stacks/miniflux/starter-feeds.opml

@@ -12,7 +12,7 @@
                xmlUrl="https://lobste.rs/rss"
                htmlUrl="https://lobste.rs/" />
     </outline>
-    <outline text="Subreddits — selfhosting / homelab / LLM" title="Subreddits — selfhosting">
+    <outline text="Subreddits — selfhosting / homelab / LLM / image-gen" title="Subreddits — selfhosting">
       <outline type="rss" text="r/selfhosted" title="r/selfhosted"
                xmlUrl="https://www.reddit.com/r/selfhosted/.rss"
                htmlUrl="https://www.reddit.com/r/selfhosted" />
@@ -22,6 +22,15 @@
       <outline type="rss" text="r/LocalLLaMA" title="r/LocalLLaMA"
                xmlUrl="https://www.reddit.com/r/LocalLLaMA/.rss"
                htmlUrl="https://www.reddit.com/r/LocalLLaMA" />
+      <outline type="rss" text="r/comfyui" title="r/comfyui"
+               xmlUrl="https://www.reddit.com/r/comfyui/.rss"
+               htmlUrl="https://www.reddit.com/r/comfyui" />
+      <outline type="rss" text="r/StableDiffusion" title="r/StableDiffusion"
+               xmlUrl="https://www.reddit.com/r/StableDiffusion/.rss"
+               htmlUrl="https://www.reddit.com/r/StableDiffusion" />
+      <outline type="rss" text="r/singularity" title="r/singularity"
+               xmlUrl="https://www.reddit.com/r/singularity/.rss"
+               htmlUrl="https://www.reddit.com/r/singularity" />
     </outline>
     <outline text="Subreddits — sports (apply spoiler block-list, see README)" title="Subreddits — sports">
       <outline type="rss" text="r/nba" title="r/nba"