Add camera module: drive UVC webcam controls via cameractrls

New `camera` module in modules.example.yaml (and the embedded copy) with
four functions: `set` (any control=value list, incl. preset/colour buttons),
`toggle` (flip between two values), `adjust` (step a numeric control by a
delta, clamped to the min/max parsed from `cameractrls -l`, with optional
`extra` controls applied first), and `is` (poll helper, exit 0 on match).

Device comes from CAMERA_DEVICE in .env (default /dev/video0) or a per-key
`device` param. cameractrls exits 0 for unknown controls, so polls must
use `is`; stderr is discarded to drop Python deprecation warnings.

README: Camera module section with setup, function table, a folder
example, and the oksvg viewBox-offset centring gotcha for SVG icons.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017iodiNMYL9iuT7f6WCe5iv

modules.example.yaml

@@ -206,3 +206,67 @@ modules:
         {{envDefault "OBS_CMD" "/usr/local/bin/obs-cmd"}} --websocket obsws://{{envDefault "OBS_HOST" "localhost"}}:{{envDefault "OBS_PORT" "4455"}}/{{env "OBS_WEBSOCKET_PASSWORD"}} scene transition-set "{{.transition}}" && \
         {{envDefault "OBS_CMD" "/usr/local/bin/obs-cmd"}} --websocket obsws://{{envDefault "OBS_HOST" "localhost"}}:{{envDefault "OBS_PORT" "4455"}}/{{env "OBS_WEBSOCKET_PASSWORD"}} scene transition-duration {{.duration}} && \
         {{envDefault "OBS_CMD" "/usr/local/bin/obs-cmd"}} --websocket obsws://{{envDefault "OBS_HOST" "localhost"}}:{{envDefault "OBS_PORT" "4455"}}/{{env "OBS_WEBSOCKET_PASSWORD"}} scene switch "{{.scene}}"
+
+  # ---------------------------------------------------------------------------
+  # Camera — cameractrls (https://github.com/soyersoyer/cameractrls), Linux only.
+  #
+  # Drives any UVC webcam's V4L2 controls (zoom, pan/tilt, focus, exposure, white
+  # balance, brightness/contrast/...). Install: pacman -S cameractrls / pip.
+  #
+  # Device: set CAMERA_DEVICE in ~/.config/streamdeck-go/.env to the stable path, e.g.
+  #   CAMERA_DEVICE=/dev/v4l/by-id/usb-046d_Logitech_BRIO_XXXX-video-index0
+  # (defaults to /dev/video0; any function also takes a per-key `device` param).
+  #
+  # Discover control names/ranges:  cameractrls -d /dev/video0 -l
+  # Note: cameractrls exits 0 even for unknown controls, so poll blocks must use
+  # the `is` function (which greps `-l` output) rather than exit codes.
+  camera:
+    # Set one or more controls, comma-separated (eg. "zoom_absolute=150,contrast=140").
+    # Buttons work too: "preset=save_1", "preset=load_1", "color_preset=vivid".
+    set:
+      params:
+        device: ""
+        controls: "zoom_absolute=100"
+      exec: /usr/bin/cameractrls -d {{if .device}}{{.device}}{{else}}{{envDefault "CAMERA_DEVICE" "/dev/video0"}}{{end}} -c "{{.controls}}" 2>/dev/null
+
+    # Flip a control between two values (a <-> b). Works for 0/1 and menu controls.
+    toggle:
+      params:
+        device: ""
+        control: auto_exposure
+        a: aperture_priority_mode
+        b: manual_mode
+      exec: |
+        cur=$(/usr/bin/cameractrls -d {{if .device}}{{.device}}{{else}}{{envDefault "CAMERA_DEVICE" "/dev/video0"}}{{end}} -l 2>/dev/null | sed -n 's/^ {{.control}} = \([^[:space:]]*\).*/\1/p')
+        if [ "$cur" = "{{.a}}" ]; then v="{{.b}}"; else v="{{.a}}"; fi
+        /usr/bin/cameractrls -d {{if .device}}{{.device}}{{else}}{{envDefault "CAMERA_DEVICE" "/dev/video0"}}{{end}} -c "{{.control}}=$v" 2>/dev/null
+
+    # Step a numeric control by delta (negative to decrease), clamped to its min/max.
+    # `extra` is applied first on the same call — eg. "auto_exposure=manual_mode"
+    # so stepping exposure also takes the camera out of auto.
+    adjust:
+      params:
+        device: ""
+        control: contrast
+        delta: "16"
+        extra: ""
+      exec: |
+        line=$(/usr/bin/cameractrls -d {{if .device}}{{.device}}{{else}}{{envDefault "CAMERA_DEVICE" "/dev/video0"}}{{end}} -l 2>/dev/null | grep '^ {{.control}} = ')
+        cur=$(printf '%s\n' "$line" | sed -n 's/^ [a-z0-9_]* = \([-0-9]*\).*/\1/p')
+        min=$(printf '%s\n' "$line" | sed -n 's/.*min: \([-0-9]*\).*/\1/p')
+        max=$(printf '%s\n' "$line" | sed -n 's/.*max: \([-0-9]*\).*/\1/p')
+        [ -n "$cur" ] || exit 1
+        v=$((cur + {{.delta}}))
+        [ -n "$min" ] && [ "$v" -lt "$min" ] && v=$min
+        [ -n "$max" ] && [ "$v" -gt "$max" ] && v=$max
+        ctl="{{.control}}=$v"
+        [ -n "{{.extra}}" ] && ctl="{{.extra}},$ctl"
+        /usr/bin/cameractrls -d {{if .device}}{{.device}}{{else}}{{envDefault "CAMERA_DEVICE" "/dev/video0"}}{{end}} -c "$ctl" 2>/dev/null
+
+    # Poll helper for toggle keys: exit 0 when control == value.
+    is:
+      params:
+        device: ""
+        control: auto_exposure
+        value: aperture_priority_mode
+      exec: /usr/bin/cameractrls -d {{if .device}}{{.device}}{{else}}{{envDefault "CAMERA_DEVICE" "/dev/video0"}}{{end}} -l 2>/dev/null | grep -q '^ {{.control}} = {{.value}}[[:space:]]'