feat: integrate Starlark/Tronbyte app support into plugin system

Add starlark-apps plugin that renders Tidbyt/Tronbyte .star apps via
Pixlet binary and integrates them into the existing Plugin Manager UI
as virtual plugins. Includes vegas scroll support, Tronbyte repository
browsing, and per-app configuration.

- Extract working starlark plugin code from starlark branch onto fresh main
- Fix plugin conventions (get_logger, VegasDisplayMode, BasePlugin)
- Add 13 starlark API endpoints to api_v3.py (CRUD, browse, install, render)
- Virtual plugin entries (starlark:<app_id>) in installed plugins list
- Starlark-aware toggle and config routing in pages_v3.py
- Tronbyte repository browser section in Plugin Store UI
- Pixlet binary download script (scripts/download_pixlet.sh)

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

scripts/download_pixlet.sh

@@ -0,0 +1,139 @@
+#!/bin/bash
+#
+# Download Pixlet binaries for bundled distribution
+#
+# This script downloads Pixlet binaries from the Tronbyte fork
+# for multiple architectures to support various platforms.
+
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_ROOT="$(dirname "$SCRIPT_DIR")"
+BIN_DIR="$PROJECT_ROOT/bin/pixlet"
+
+# Pixlet version to download (use 'latest' to auto-detect)
+PIXLET_VERSION="${PIXLET_VERSION:-latest}"
+
+# GitHub repository (Tronbyte fork)
+REPO="tronbyt/pixlet"
+
+echo "========================================"
+echo "Pixlet Binary Download Script"
+echo "========================================"
+
+# Auto-detect latest version if needed
+if [ "$PIXLET_VERSION" = "latest" ]; then
+    echo "Detecting latest version..."
+    PIXLET_VERSION=$(curl -s "https://api.github.com/repos/${REPO}/releases/latest" | grep '"tag_name"' | sed -E 's/.*"([^"]+)".*/\1/')
+    if [ -z "$PIXLET_VERSION" ]; then
+        echo "Failed to detect latest version, using fallback"
+        PIXLET_VERSION="v0.50.2"
+    fi
+fi
+
+echo "Version: $PIXLET_VERSION"
+echo "Target directory: $BIN_DIR"
+echo ""
+
+# Create bin directory if it doesn't exist
+mkdir -p "$BIN_DIR"
+
+# New naming convention: pixlet_v0.50.2_linux-arm64.tar.gz
+# Only download ARM64 Linux binary for Raspberry Pi
+declare -A ARCHITECTURES=(
+    ["linux-arm64"]="pixlet_${PIXLET_VERSION}_linux-arm64.tar.gz"
+)
+
+download_binary() {
+    local arch="$1"
+    local archive_name="$2"
+    local binary_name="pixlet-${arch}"
+
+    local output_path="$BIN_DIR/$binary_name"
+
+    # Skip if already exists
+    if [ -f "$output_path" ]; then
+        echo "✓ $binary_name already exists, skipping..."
+        return 0
+    fi
+
+    echo "→ Downloading $arch..."
+
+    # Construct download URL
+    local url="https://github.com/${REPO}/releases/download/${PIXLET_VERSION}/${archive_name}"
+
+    # Download to temp directory (use project-local temp to avoid /tmp permission issues)
+    local temp_dir
+    temp_dir=$(mktemp -d -p "$PROJECT_ROOT" -t pixlet_download.XXXXXXXXXX)
+    local temp_file="$temp_dir/$archive_name"
+
+    if ! curl -L -o "$temp_file" "$url" 2>/dev/null; then
+        echo "✗ Failed to download $arch"
+        rm -rf "$temp_dir"
+        return 1
+    fi
+
+    # Extract binary
+    echo "  Extracting..."
+    if ! tar -xzf "$temp_file" -C "$temp_dir"; then
+        echo "✗ Failed to extract archive: $temp_file"
+        rm -rf "$temp_dir"
+        return 1
+    fi
+
+    # Find the pixlet binary in extracted files
+    local extracted_binary
+    extracted_binary=$(find "$temp_dir" -name "pixlet" | head -n 1)
+
+    if [ -z "$extracted_binary" ]; then
+        echo "✗ Binary not found in archive"
+        rm -rf "$temp_dir"
+        return 1
+    fi
+
+    # Move to final location
+    mv "$extracted_binary" "$output_path"
+
+    # Make executable
+    chmod +x "$output_path"
+
+    # Clean up
+    rm -rf "$temp_dir"
+
+    # Verify
+    local size
+    size=$(stat -f%z "$output_path" 2>/dev/null || stat -c%s "$output_path" 2>/dev/null || echo "unknown")
+    if [ "$size" = "unknown" ]; then
+        echo "✓ Downloaded $binary_name"
+    else
+        echo "✓ Downloaded $binary_name ($(numfmt --to=iec-i --suffix=B $size 2>/dev/null || echo "${size} bytes"))"
+    fi
+
+    return 0
+}
+
+# Download binaries for each architecture
+success_count=0
+total_count=${#ARCHITECTURES[@]}
+
+for arch in "${!ARCHITECTURES[@]}"; do
+    if download_binary "$arch" "${ARCHITECTURES[$arch]}"; then
+        ((success_count++))
+    fi
+done
+
+echo ""
+echo "========================================"
+echo "Download complete: $success_count/$total_count succeeded"
+echo "========================================"
+
+# List downloaded binaries
+echo ""
+echo "Installed binaries:"
+if compgen -G "$BIN_DIR/*" > /dev/null 2>&1; then
+    ls -lh "$BIN_DIR"/*
+else
+    echo "No binaries found"
+fi
+
+exit 0