feat(lora): add dynamic coding rate policy

[Komzpa]

Summary

Adds a first firmware implementation of Dynamic Coding Rate as a shared AirtimePolicy instead of backend-local heuristics.

• classifies packets by port/priority and chooses CR 4/5 through CR 4/8 from packet class, channel pressure, retry context, relay context, duty-cycle pressure, airtime caps, and a CR 4/8 token bucket
• applies per-packet CR through the common radio layer for RadioLib radios and the Portduino simulator, then restores the configured base CR after TX
• observes RX coding rate from the RadioLib header path and keeps local counters / neighbor attribution without adding a MeshPacket field
• records failed retransmissions with the actual last TX CR for that packet
• treats retry losses as quiet only below an actual selected-region duty-cycle limit when one applies; unrestricted or duty-cycle-overridden regions do not get a synthetic quiet-loss utilization threshold
• prevents final-retry quiet-loss escalation while the policy already considers the channel busy or congested
• keeps reused packet storage from reusing stale packet-class cache entries
• preserves LR11x0/LR20x0/SX128x long-interleaving static configuration when restoring the base coding rate after a DCR transmit
• adds generated LoRa config fields, docs, and native policy tests

Dependency

Depends on meshtastic/protobufs#902 for the source LoRaConfig fields. The firmware submodule pointer is intentionally not advanced in this PR; only the generated firmware-side protobuf files are included here.

Rollout Notes

DCR is a simple on/off policy gate: DCR_OFF keeps the configured static coding rate, and DCR_ON applies per-packet coding-rate selection. There is no observe-only mode, and this PR does not reserve debug/capability fields that are not consumed by the firmware.

Hardware interop still needs real-radio validation across SX126x, SX127x/RF95, SX128x, LR11x0, static-CR nodes, and mixed DCR/static relays.

Tests

• git diff --check
• ./bin/test-native-docker.sh -f test_dynamic_coding_rate (16/16)
• Docker PlatformIO build: platformio run -e heltec-v3
• Docker PlatformIO build: platformio run -e tbeam

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: compile-only validation for heltec-v3 and tbeam; native Portduino policy tests pass. Real-radio interop remains pending as noted above.