Rewrite Miniflux plugin to use requests, add filter and bookmark tools

Drop the miniflux pip client in favour of requests (already in the
container). Add update_feed_filters (keeplist/blocklist regex),
toggle_bookmark, get_entry (full content), and category filtering.
Remove the pip install step from Ansible.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

infra/hermes/plugins/miniflux/plugin.yaml

@@ -1,6 +1,10 @@
 name: miniflux
-version: 1.0.0
-description: Read feeds and entries from the local Miniflux RSS reader
+version: 2.0.0
+description: Read and manage feeds and entries from the local Miniflux RSS reader
 provides_tools:
   - list_feeds
   - get_unread_entries
+  - get_entry
+  - toggle_bookmark
+  - update_feed_filters
+  - mark_as_read