fix(web): accept every panel size and row address type the rgbmatrix library does

The Display form capped columns at 128 and chain length at 24, and its
submit handler (fixInvalidNumberInputs) rewrote anything larger to the cap,
so wide panels and long chains silently saved as the wrong size. The config
API checked none of the hardware numbers, so values the library rejects (odd
rows, parallel 4, PWM dither bits 3) saved and the matrix then refused to
start.

- Form limits now match the pinned library: rows even 8-64, cols >= 16 and
  chain_length >= 1 with no upper bound, parallel 1-3, PWM dither bits 0-2,
  PWM LSB nanoseconds 50-3000.
- save_main_config rejects out-of-range rows, cols, chain_length, parallel,
  brightness, scan_mode, pwm_bits, pwm_dither_bits, pwm_lsb_nanoseconds and
  gpio_slowdown with a 400.
- A stored gpio_slowdown or pwm_dither_bits of 0 renders as 0 instead of the
  default, so saving the tab no longer overwrites it.
- Row Address Type offers 5 (SM5368 / B707 row shift register). Verified on a
  Waveshare 96x48 V2 (24S-A1) on a Pi 4 with the Adafruit Triple LED Matrix
  Bonnet: rows 48, cols 96, row address type 5, BGR, GPIO slowdown 8.
- Help text and docs: FM6124-family panels use Panel Type Standard; on a Pi 5
  the library supports only row address types 0 and 2.

No change to the rpi-rgb-led-matrix submodule.

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

docs/CONFIG_REFERENCE.md

@@ -51,15 +51,15 @@ in `DisplayManager` (`src/display_manager.py`, ~lines 270–295).
 
 | Key | Type / default |
 |---|---|
-| `rows` / `cols` | int, `32` / `64` |
-| `chain_length` | int, `2` |
-| `parallel` | int, `1` |
-| `brightness` | int, `90` |
+| `rows` / `cols` | int, `32` / `64` — rows: even, 8–64; cols: at least 16, no upper limit |
+| `chain_length` | int, `2` — at least 1, no upper limit |
+| `parallel` | int, `1` — 1–3 |
+| `brightness` | int, `90` — 1–100 |
 | `hardware_mapping` | string, `"adafruit-hat"` (code default `"adafruit-hat-pwm"`) |
-| `scan_mode` | int, `0` |
-| `pwm_bits` | int, `9` (code default 10) |
-| `pwm_dither_bits` | int, `1` |
-| `pwm_lsb_nanoseconds` | int, `130` (code default 150) |
+| `scan_mode` | int, `0` — `0` progressive, `1` interlaced |
+| `pwm_bits` | int, `9` (code default 10) — 1–11 |
+| `pwm_dither_bits` | int, `1` — 0–2 |
+| `pwm_lsb_nanoseconds` | int, `130` (code default 150) — 50–3000 |
 | `disable_hardware_pulsing` | bool, `false` |
 | `inverse_colors` | bool, `false` |
 | `show_refresh_rate` | bool, `false` |
@@ -67,9 +67,9 @@ in `DisplayManager` (`src/display_manager.py`, ~lines 270–295).
 | `limit_refresh_rate_hz` | int, `100` (code default 90) |
 | `pixel_mapper_config` | string, `""` — e.g. `"U-mapper"` / `"Rotate:90"` |
 | `orientation` | string, `"normal"` — `"180"` rotates the rendered image 180° for panels physically mounted upside down (e.g. to move the Pi/wiring to a more convenient side); composed onto `pixel_mapper_config` as a trailing `Rotate:180` mapper, so it stays independent of any custom `pixel_mapper_config` value |
-| `row_address_type` | int, `0` — non-standard panel row addressing |
+| `row_address_type` | int, `0` — non-standard panel row addressing: `1` AB, `2` direct row select, `3` ABC, `4` ABC shift + DE direct, `5` SM5368 / B707 row shift register (e.g. Waveshare 96x48 V2, with `led_rgb_sequence` `"BGR"`). On a Pi 5 the library supports only `0` and `2` |
 | `multiplexing` | int, `0` — panel multiplexing scheme |
-| `panel_type` | string, `""` — set to `"FM6126A"` or `"FM6127"` for panels needing init |
+| `panel_type` | string, `""` — set to `"FM6126A"` or `"FM6127"` for panels needing init; FM6124 / FM6124D / FM6124DJ panels need none, so leave it `""` |
 
 Where "code default" differs from the template value, the code default only
 applies if the key is missing entirely from your config.
@@ -78,7 +78,7 @@ applies if the key is missing entirely from your config.
 
 | Key | Type / default | Meaning |
 |---|---|---|
-| `gpio_slowdown` | int, `3` | GPIO timing slowdown for faster Pis |
+| `gpio_slowdown` | int, `3` | GPIO timing slowdown for faster Pis (0–10). Panels on `row_address_type` `5` (SM5368 row drivers) can need 6–8 on a Pi 4 — lower values make rows jump |
 | `rp1_rio` | int, `0` | RP1 RIO mode on Pi 5 (applied only if the installed matrix library supports it) |
 
 ## `display.double_sided`

docs/GETTING_STARTED.md

@@ -83,10 +83,10 @@ You should see:
 
 1. Open the **Display** tab
 2. Set your matrix configuration:
-   - **Rows**: 32 or 64 (match your hardware)
-   - **Columns**: commonly 64 or 96; the web UI accepts any integer
-     in the 1–128 range, but 64 and 96 are the values the bundled
-     panel hardware ships with
+   - **Rows**: match your panel — commonly 32 or 64; any even number
+     from 8 to 64
+   - **Columns**: match your panel — commonly 64 or 96; at least 16,
+     with no upper limit
    - **Chain Length**: Number of panels chained horizontally
    - **Hardware Mapping**: usually `adafruit-hat-pwm` (with the PWM jumper
      mod) or `adafruit-hat` (without). See the root README for the full list.