chore(deps): update rpi-rgb-led-matrix to latest upstream for Pi 5 support

Configure submodule to track upstream master branch (branch = master in
.gitmodules) so future updates are a single 'git submodule update --remote'
rather than manual SHA management.

Update first_time_install.sh to use --remote flag so fresh installs always
pull the current upstream master, not the commit recorded at clone time.

Current upstream HEAD (8907235) brings:
- PR #1886: Raspberry Pi 5 support — new RP1 PIO and RIO backends. The
  library auto-detects Pi 5 hardware at runtime; no config change required
  for basic operation. adafruit-hat-pwm is confirmed supported on Pi 5.
- PR #1833: setup.py migrated from distutils → setuptools, fixing Python
  3.12+ build failure (Pi runs Python 3.13). Previous version could not
  build the bindings at all on current Pi OS.

Expose new rp1_rio option in display_manager.py and config.template.json:
  0 (default) = PIO mode — uses Pi 5 RP1 coprocessor, minimal CPU usage
  1 = RIO mode — Registered IO, faster throughput, higher CPU; note that
      gpio_slowdown has inverted effect in this mode

No API changes to RGBMatrix, RGBMatrixOptions, or FrameCanvas. Pi 4 and
earlier hardware is unaffected — rp1_rio is silently ignored on non-Pi-5.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitmodules

@@ -1,3 +1,4 @@
 [submodule "rpi-rgb-led-matrix-master"]
 	path = rpi-rgb-led-matrix-master
 	url = https://github.com/hzeller/rpi-rgb-led-matrix.git
+	branch = master

config/config.template.json

@@ -112,7 +112,8 @@
             "limit_refresh_rate_hz": 100
         },
         "runtime": {
-            "gpio_slowdown": 3
+            "gpio_slowdown": 3,
+            "rp1_rio": 0
         },
         "display_durations": {},
         "use_short_date_format": true,

first_time_install.sh

@@ -795,7 +795,7 @@ else
         # Try to initialize submodule if .gitmodules exists
         if [ -f "$PROJECT_ROOT_DIR/.gitmodules" ] && grep -q "rpi-rgb-led-matrix" "$PROJECT_ROOT_DIR/.gitmodules"; then
             echo "Initializing rpi-rgb-led-matrix submodule..."
-            if ! git submodule update --init --recursive rpi-rgb-led-matrix-master 2>&1; then
+            if ! git submodule update --init --remote --recursive rpi-rgb-led-matrix-master 2>&1; then
                 echo "⚠ Submodule init failed, cloning directly from GitHub..."
                 git clone https://github.com/hzeller/rpi-rgb-led-matrix.git rpi-rgb-led-matrix-master
             fi
@@ -814,7 +814,7 @@ else
             cd "$PROJECT_ROOT_DIR"
             rm -rf rpi-rgb-led-matrix-master
             if [ -f "$PROJECT_ROOT_DIR/.gitmodules" ] && grep -q "rpi-rgb-led-matrix" "$PROJECT_ROOT_DIR/.gitmodules"; then
-                git submodule update --init --recursive rpi-rgb-led-matrix-master
+                git submodule update --init --remote --recursive rpi-rgb-led-matrix-master
             else
                 git clone https://github.com/hzeller/rpi-rgb-led-matrix.git rpi-rgb-led-matrix-master
             fi

src/display_manager.py

@@ -100,6 +100,10 @@ class DisplayManager:
                 options.pwm_dither_bits = hardware_config.get('pwm_dither_bits')
             if 'inverse_colors' in hardware_config:
                 options.inverse_colors = hardware_config.get('inverse_colors')
+            # Pi 5 only: 0=PIO/RP1 coprocessor (default, less CPU),
+            # 1=RIO/Registered IO (faster; gpio_slowdown effect is inverted in this mode)
+            if 'rp1_rio' in runtime_config:
+                options.rp1_rio = runtime_config.get('rp1_rio')
             
             logger.info(f"Initializing RGB Matrix with settings: rows={options.rows}, cols={options.cols}, chain_length={options.chain_length}, parallel={options.parallel}, hardware_mapping={options.hardware_mapping}")