modules: fix broadcasting neighbor info

[l5yth]

• NeighborInfoModule now schedules its first run 35 s after boot as documented, instead of waiting for the full configured interval. Scratched that.
• Neighbor broadcasts are emitted every cycle regardless of the currently known neighbor count, with an inline comment explaining why we keep sending empty payloads to bootstrap future discovery. This reverts Only send Neighbours if we have some to send. #7493
• Neighbor cleanup is more forgiving: entries fall back to min_node_info_broadcast_secs when no interval is known and are only purged after 4× that duration, preventing premature eviction when RX is spotty.
• getOrCreateNeighbor() now normalizes zero-interval updates to min_node_info_broadcast_secs, ensuring we never store a 0 s interval that would trigger immediate cleanup, while still honoring explicit intervals from peers.
• attempt to fix [Bug]: NeighborInfoApp stopped broadcasting over LoRa #8581

🤝 Attestations

• I have tested that my proposed changes behave as described.
• I have tested that my proposed changes do not cause any obvious regressions on the following devices:
  • Heltec (Lora32) V3
  • LilyGo T-Deck
  • LilyGo T-Beam
  • RAK WisBlock 4631
  • Seeed Studio T-1000E tracker card
  • Other (please specify below)

These changes are untested as I want to gather feedback on the proposed changes first. I'm currently testing this on my hardware. ⏳