feat: refuse matrix settings a Raspberry Pi 5 can't drive

On a Pi 5 the pinned rgbmatrix library drives the panel through the RP1
chip, and that path supports only row address types 0 and 2, parallel 1-3
and the regular / regular-pi1 / classic / adafruit-hat(-pwm) mappings
(Rp1PioConfigSupported in lib/rp1/rp1_pio_backend.cc). For anything else
CreateFromOptions returns NULL; the Python binding doesn't check, so the
display process crashed on its first call into the matrix and systemd
restarted it into the same crash every 10 seconds.

- src/pi5_matrix_support.py: the rule and Pi 5 detection, matching the
  library's /proc/device-tree/model check
- DisplayManager raises before creating the matrix, so it is a logged init
  failure (reported by /api/v3/hardware/status) and fallback mode
- the config API rejects those settings on a Pi 5 when a request sets
  row_address_type, parallel or hardware_mapping
- the Display form offers only row address types 0 and 2 on a Pi 5, and
  warns when a stored value can't be used
- CLAUDE.md: re-check the rule whenever the submodule is bumped

Review feedback on #586.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

CLAUDE.md

@@ -63,3 +63,4 @@
   `self.display_manager.image.paste(img, (x, y))` then `update_display()`
   (use a mask for transparency: `image.paste(rgba, (x, y), rgba)`)
 - When modifying a plugin in the monorepo, you MUST bump `version` in its `manifest.json` and run `python update_registry.py` — otherwise users won't receive the update
+- `src/pi5_matrix_support.py` hardcodes what the pinned `rpi-rgb-led-matrix-master` can drive on a Raspberry Pi 5 (`Rp1PioConfigSupported()` in `lib/rp1/rp1_pio_backend.cc`). Re-check it whenever the submodule is bumped: a stale rule blocks Pi 5 settings the new library supports, and a missing one lets the display service crash-loop