M1+M2 hardware bring-up: 3 fixes + elegant subsystem degradation

First flash to real hardware (Waveshare ESP32-P4-ETH on USB power,
no LAN cable, no panel attached) exposed three bugs and the need to
degrade gracefully when peripherals are missing.

1. net_eth.c: RXD0 / RXD1 GPIO swap. ESP32-P4's EMAC iomux table
   (components/soc/esp32p4/emac_periph.c) fixes RXD0 to GPIO 29 and
   RXD1 to GPIO 30. The Waveshare-wiki/ESPHome research had them
   transposed. Symptom was:
     E (esp.emac.gpio): invalid RXD0 GPIO number
     E (esp.emac): esp_eth_mac_new_esp32 failed
     -> ESP_ERROR_CHECK abort
   Fix: swap the two #defines. CRS_DV / TXD0 / TXD1 / TX_EN / REF_CLK
   pinout was already correct.

2. mdns_service.c: mdns_service_add() rejects with INVALID_ARG when
   the hostname isn't set yet (see mdns_responder.c:771 — first guard
   in mdns_service_add_for_host). We were setting hostname AFTER
   service_add inside apply_records(). Restructure mdns_service_start
   to: init -> hostname -> service_add -> txt. apply_hostname() and
   apply_txt() helpers reuse the same snapshot under viewport_state's
   mutex; mdns_service_refresh() re-applies both.

3. app_main.c: every subsystem now best-effort instead of
   ESP_ERROR_CHECK abort. A single missing peripheral can't take down
   the rest of the firmware. End-of-boot summary line:
     boot complete — subsystems [EMHdJ-B]  ip=(no link)
   Uppercase letter = up, lowercase = down. E=Ethernet M=mDNS H=HTTP
   D=Display J=JPEG T=Touch B=BootButton. Touch shows '-' when display
   didn't come up (it shares the panel I2C bus). On a stripped board
   (just ESP32-P4-ETH on USB, no panel, no LAN) the line above prints
   and the device serves /state, /config, and mDNS over the loopback;
   plugging Ethernet in later picks up DHCP without a reboot.

Side-effects: the DHCP timeout in app_main shortened from 30s to 15s
so a no-cable boot finishes quickly. Reaching the "ready" state with
no link is fine — the driver keeps the link-up event handler armed and
gets the IP whenever a cable appears.

Verified on hardware (bare ESP32-P4-ETH, no LAN, no panel):
- ESP-IDF v5.4.1, esp32p4, 32 MB PSRAM detected, 16 MB flash config
  (actual 32 MB silkscreen — keeping 16 MB until access-beyond-16MB
  support lands in flash driver).
- Ethernet driver started — MAC e8:f6:0a:e0:90:94.
- mDNS up advertising viewport.local on _scrypted-viewport._tcp:80.
- HTTP up listening :80.
- JPEG decoder ready.
- Display reports "panel MCU @0x45 unreachable" — exactly correct
  for no-panel state.
- Touch skipped as designed.
- BOOT button registered on GPIO 0 (still a guess; harmless if wrong).

This is enough to flip M1's "code" status to ✅ on hardware once
Ethernet is plugged in. M2 (mDNS browse + GET /state) ready to verify.

1 files changed, 3 insertions, 1 deletions

diff --git a/README.md b/README.md
index 3723596..17d346c 100644
--- a/README.md
+++ b/README.md
@@ -4,7 +4,9 @@ Version: 1.0
 
 ## Overview
 
-Scrypted Viewport is an Ethernet-powered ambient display appliance optimized for Scrypted camera and doorbell events.
+Scrypted Viewport is an Ethernet-powered ambient display appliance optimized for Scrypted camera and doorbell
+events. It's meant to be plug and play onto a trusted POE VLAN connection with Scrypted access so there's no
+configuration done on the esp32 itself and instead is discoverd and configured within Scrypted.
 
 Design goals:
 - No Matter