fix(web): drop the rows cap and document every display setting accurately

Rows: no upper limit in the form or the API. Still even and at least 8. The
current rgbmatrix library rejects more than 64 per panel, so a larger value
saves but the matrix won't start; the help tip, README, config reference and
troubleshooting section all say so, and nothing here needs changing if the
library lifts the limit.

limit_refresh_rate_hz: the form accepts 0 (the library's "no cap"), a stored
0 no longer renders and re-saves as 120, and the API rejects negatives.

pwm_dither_bits stays 0-2: the library rejects 3 and 4, so the old form's
0-4 only ever let users save a config the display couldn't start with.

Docs and help tips, checked against the pinned library and its README:
- panel_type and rp1_rio get README entries
- show_refresh_rate prints to stdout; it never drew on the panel
- dither bits raise the refresh rate; the tip said they lowered it
- scan_mode is about interlacing at low refresh, not wrong colours
- disable_hardware_pulsing: hardware pulsing needs OE on GPIO 18 and the
  onboard sound driver off; software timing makes rows flash brighter
- gpio_slowdown guidance agrees between the README and the UI
- all 22 multiplexing values listed; every numeric setting states its range
- troubleshooting for a blank panel after a settings change, jumping rows
  and brightness flashes

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

docs/CONFIG_REFERENCE.md

@@ -51,7 +51,7 @@ in `DisplayManager` (`src/display_manager.py`, ~lines 270–295).
 
 | Key | Type / default |
 |---|---|
-| `rows` / `cols` | int, `32` / `64` — rows: even, 8–64; cols: at least 16, no upper limit |
+| `rows` / `cols` | int, `32` / `64` — rows: even, at least 8, no upper limit here (the current rgbmatrix library rejects more than 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 |
@@ -60,15 +60,15 @@ in `DisplayManager` (`src/display_manager.py`, ~lines 270–295).
 | `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` |
+| `disable_hardware_pulsing` | bool, `false` — `true` times brightness pulses in software (less exact); hardware pulsing needs the OE line on GPIO 18 and the Pi's onboard sound driver off |
 | `inverse_colors` | bool, `false` |
-| `show_refresh_rate` | bool, `false` |
-| `led_rgb_sequence` | string, `"RGB"` |
-| `limit_refresh_rate_hz` | int, `100` (code default 90) |
+| `show_refresh_rate` | bool, `false` — prints the refresh rate to stdout; draws nothing on the panel |
+| `led_rgb_sequence` | string, `"RGB"` — `"RGB"`, `"RBG"`, `"GRB"`, `"GBR"`, `"BRG"` or `"BGR"` |
+| `limit_refresh_rate_hz` | int, `100` (code default 90) — `0` = no cap; scroll timing assumes 100 Hz when `0` |
 | `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: `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 |
+| `multiplexing` | int, `0` — 0–22, pixel wiring scheme for outdoor/specialty panels (names listed in the README) |
 | `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
@@ -79,7 +79,7 @@ applies if the key is missing entirely from your config.
 | Key | Type / default | Meaning |
 |---|---|---|
 | `gpio_slowdown` | int, `3` | GPIO timing slowdown for faster Pis (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) |
+| `rp1_rio` | int, `0` | Pi 5 only: `0` = PIO (less CPU), `1` = RIO (higher refresh; `gpio_slowdown` effect inverted). Applied only if the installed matrix library supports it |
 
 ## `display.double_sided`