feat: add Linux tarball and Docker image to release workflow

Restructure release.yml into 4 jobs:
- create-release: shared Gitea release with download table
- build-windows: existing portable ZIP (unchanged)
- build-linux: new tarball with venv + run.sh launcher
- build-docker: push image to Gitea Container Registry

Add build-dist.sh as Linux equivalent of build-dist.ps1.
Docker tags: version + latest (stable only, no latest for alpha/beta/rc).

build-dist.sh

@@ -0,0 +1,133 @@
+#!/usr/bin/env bash
+#
+# Build a portable Linux distribution of LedGrab.
+# Produces a self-contained tarball with virtualenv and launcher script.
+#
+# Usage:
+#   ./build-dist.sh [VERSION]
+#   ./build-dist.sh v0.1.0-alpha.1
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+BUILD_DIR="$SCRIPT_DIR/build"
+DIST_NAME="LedGrab"
+DIST_DIR="$BUILD_DIR/$DIST_NAME"
+SERVER_DIR="$SCRIPT_DIR/server"
+VENV_DIR="$DIST_DIR/venv"
+APP_DIR="$DIST_DIR/app"
+
+# ── Version detection ────────────────────────────────────────
+
+VERSION="${1:-}"
+
+if [ -z "$VERSION" ]; then
+    VERSION=$(git describe --tags --exact-match 2>/dev/null || true)
+fi
+if [ -z "$VERSION" ]; then
+    VERSION="${GITEA_REF_NAME:-${GITHUB_REF_NAME:-}}"
+fi
+if [ -z "$VERSION" ]; then
+    VERSION=$(grep -oP '__version__\s*=\s*"\K[^"]+' "$SERVER_DIR/src/wled_controller/__init__.py" 2>/dev/null || echo "0.0.0")
+fi
+
+VERSION_CLEAN="${VERSION#v}"
+TAR_NAME="LedGrab-v${VERSION_CLEAN}-linux-x64.tar.gz"
+
+echo "=== Building LedGrab v${VERSION_CLEAN} (Linux) ==="
+echo "  Output: build/$TAR_NAME"
+echo ""
+
+# ── Clean ────────────────────────────────────────────────────
+
+if [ -d "$DIST_DIR" ]; then
+    echo "[1/7] Cleaning previous build..."
+    rm -rf "$DIST_DIR"
+fi
+mkdir -p "$DIST_DIR"
+
+# ── Create virtualenv ────────────────────────────────────────
+
+echo "[2/7] Creating virtualenv..."
+python3 -m venv "$VENV_DIR"
+source "$VENV_DIR/bin/activate"
+pip install --upgrade pip --quiet
+
+# ── Install dependencies ─────────────────────────────────────
+
+echo "[3/7] Installing dependencies..."
+pip install --quiet "${SERVER_DIR}[camera,notifications]" 2>&1 | {
+    grep -i 'error\|failed' || true
+}
+
+# Remove the installed wled_controller package (PYTHONPATH handles app code)
+SITE_PACKAGES="$VENV_DIR/lib/python*/site-packages"
+rm -rf $SITE_PACKAGES/wled_controller* $SITE_PACKAGES/wled*.dist-info 2>/dev/null || true
+
+# Clean up caches
+find "$VENV_DIR" -type d -name __pycache__ -exec rm -rf {} + 2>/dev/null || true
+find "$VENV_DIR" -type d -name tests -exec rm -rf {} + 2>/dev/null || true
+find "$VENV_DIR" -type d -name test -exec rm -rf {} + 2>/dev/null || true
+
+# ── Build frontend ───────────────────────────────────────────
+
+echo "[4/7] Building frontend bundle..."
+(cd "$SERVER_DIR" && npm ci --loglevel error && npm run build) 2>&1 | {
+    grep -v 'RemoteException' || true
+}
+
+# ── Copy application files ───────────────────────────────────
+
+echo "[5/7] Copying application files..."
+mkdir -p "$APP_DIR"
+
+cp -r "$SERVER_DIR/src" "$APP_DIR/src"
+cp -r "$SERVER_DIR/config" "$APP_DIR/config"
+mkdir -p "$DIST_DIR/data" "$DIST_DIR/logs"
+
+# Clean up source maps and __pycache__
+find "$APP_DIR" -name "*.map" -delete 2>/dev/null || true
+find "$APP_DIR" -type d -name __pycache__ -exec rm -rf {} + 2>/dev/null || true
+
+# ── Create launcher ──────────────────────────────────────────
+
+echo "[6/7] Creating launcher..."
+cat > "$DIST_DIR/run.sh" << 'LAUNCHER'
+#!/usr/bin/env bash
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+
+export PYTHONPATH="$SCRIPT_DIR/app/src"
+export WLED_CONFIG_PATH="$SCRIPT_DIR/app/config/default_config.yaml"
+
+mkdir -p "$SCRIPT_DIR/data" "$SCRIPT_DIR/logs"
+
+echo ""
+echo "  ============================================="
+echo "   LedGrab vVERSION_PLACEHOLDER"
+echo "   Open http://localhost:8080 in your browser"
+echo "  ============================================="
+echo ""
+
+source "$SCRIPT_DIR/venv/bin/activate"
+exec python -m uvicorn wled_controller.main:app --host 0.0.0.0 --port 8080
+LAUNCHER
+
+sed -i "s/VERSION_PLACEHOLDER/${VERSION_CLEAN}/" "$DIST_DIR/run.sh"
+chmod +x "$DIST_DIR/run.sh"
+
+# ── Create tarball ───────────────────────────────────────────
+
+echo "[7/7] Creating $TAR_NAME..."
+deactivate 2>/dev/null || true
+
+TAR_PATH="$BUILD_DIR/$TAR_NAME"
+(cd "$BUILD_DIR" && tar -czf "$TAR_NAME" "$DIST_NAME")
+
+TAR_SIZE=$(du -h "$TAR_PATH" | cut -f1)
+echo ""
+echo "=== Build complete ==="
+echo "  Archive: $TAR_PATH"
+echo "  Size: $TAR_SIZE"
+echo ""