MESH-API v0.7.4.1 Beta - Send Composer Revamp, Previously Seen Nodes & MeshCore Presence Fix

MESH-API v0.7.4.1 Beta — Send Composer Revamp, Previously Seen Nodes & MeshCore Presence Fix

This release focuses on the dashboard Send a Message experience, node-list
presence accuracy across both radios, and a big documentation cleanup.

📤 Send a Message composer, rebuilt

• New Broadcast / Direct mode tabs replace the old single mode toggle.
• Broadcast mode now has a per-network picker with checkboxes so you can
  target one or more radios in a single send:
  • 📡 Meshtastic — pick a Meshtastic channel.
  • 🟣 MeshCore — pick a MeshCore channel.
  • 🌉 Bridged — fan out to both radios at once. The bridged dropdown
    now shows both routed channels for each entry, e.g.
    0 → 📡 LongFast + 🟣 Public, so it's clear exactly which Meshtastic and
    MeshCore channels a bridged broadcast will reach (instead of a single
    ambiguous channel name).
• Direct mode searches the combined node list across both networks and hints
  which network the selected destination lives on.
• Rows are only shown for the radios you actually have connected (the bridged
  row appears only when both Meshtastic and MeshCore are active).

🟢 "Previously Seen" nodes

• The Available Nodes panel now splits into a live list and a collapsible
  Previously Seen section for nodes that have gone quiet, controlled by an
  adjustable staleness threshold. Favorited nodes stay pinned in the main list.

🐛 MeshCore node presence fix

• MeshCore addressable contacts were incorrectly dropping into Previously Seen
  (or out of the list) because their occasional advert age was treated like
  a continuous Meshtastic beacon.
• Presence for MeshCore nodes is now activity-based — only message activity
  marks a MeshCore node as recently heard — while Meshtastic nodes keep using
  all presence signals. This matches how MeshCore works: a persistent contact
  book with only occasional adverts, rather than continuous beaconing.

📚 Documentation cleanup

• The README was slimmed substantially. Large reference sections moved into their
  own files that the README links to:
  • DEVELOPING_EXTENSIONS.md — full extension developer guide.
  • CONFIGURATION.md — complete config.json reference.
  • INTEGRATIONS.md — Home Assistant, LLM, Email, Discord, and Twilio setup.
• The dashboard footer link now points to mesh-api.dev.

Still a beta — please report anything that breaks on
GitHub Issues.