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>

web_interface/blueprints/api_v3/config.py

@@ -577,10 +577,48 @@ def save_main_config():
             if 'row_address_type' in data:
                 try:
                     rat_val = int(data['row_address_type'])
-                    if rat_val < 0 or rat_val > 4:
-                        return jsonify({'status': 'error', 'message': f"Invalid row_address_type '{data['row_address_type']}'. Must be an integer from 0 to 4."}), 400
+                    if rat_val < 0 or rat_val > 5:
+                        return jsonify({'status': 'error', 'message': f"Invalid row_address_type '{data['row_address_type']}'. Must be an integer from 0 to 5."}), 400
                 except (ValueError, TypeError, OverflowError):
-                    return jsonify({'status': 'error', 'message': f"Invalid row_address_type '{data['row_address_type']}'. Must be an integer from 0 to 4."}), 400
+                    return jsonify({'status': 'error', 'message': f"Invalid row_address_type '{data['row_address_type']}'. Must be an integer from 0 to 5."}), 400
+
+            # Panel geometry, PWM and GPIO timing, held to what the rgbmatrix library
+            # accepts (RGBMatrix::Options::Validate in lib/options-initialize.cc,
+            # the gpio_slowdown check in lib/led-matrix.cc). Outside those ranges
+            # the config used to save, then the matrix refused to start and the
+            # display dropped to fallback mode. cols and chain_length have no
+            # upper bound in the library, so none here.
+            def _hardware_int_error(field, low, high=None, even=False):
+                """A 400 response if data[field] is not an allowed integer, else None."""
+                raw = data[field]
+                if even:
+                    allowed = f"an even integer from {low} to {high}"
+                elif high is None:
+                    allowed = f"an integer of at least {low}"
+                else:
+                    allowed = f"an integer from {low} to {high}"
+                rejection = (jsonify({'status': 'error', 'message': f"Invalid {field} '{raw}'. Must be {allowed}."}), 400)
+                # int() would quietly turn true into 1 and 48.5 into 48.
+                if isinstance(raw, bool) or (isinstance(raw, float) and not raw.is_integer()):
+                    return rejection
+                try:
+                    value = int(raw)
+                except (ValueError, TypeError, OverflowError):
+                    return rejection
+                if value < low or (high is not None and value > high) or (even and value % 2):
+                    return rejection
+                return None
+
+            for field, low, high, even in (('rows', 8, 64, True), ('cols', 16, None, False),
+                                           ('chain_length', 1, None, False), ('parallel', 1, 3, False),
+                                           ('brightness', 1, 100, False), ('scan_mode', 0, 1, False),
+                                           ('pwm_bits', 1, 11, False), ('pwm_dither_bits', 0, 2, False),
+                                           ('pwm_lsb_nanoseconds', 50, 3000, False),
+                                           ('gpio_slowdown', 0, 10, False)):
+                if field in data:
+                    error = _hardware_int_error(field, low, high, even)
+                    if error:
+                        return error
 
             # Handle hardware settings
             for field in ['rows', 'cols', 'chain_length', 'parallel', 'brightness', 'hardware_mapping', 'scan_mode',