chore: enable Cerberus security by default and fix 31 skipped E2E tests

Phase 1 of skipped Playwright tests remediation:

Changed Cerberus default from disabled to enabled in backend code
Deprecated FEATURE_CERBERUS_ENABLED env var (no longer needed)
Added data-testid and a11y attributes to LanguageSelector component
Fixed keyboard navigation timing in account-settings and user-management tests
Simplified security dashboard toggle tests with waitForToast pattern
Test results: 668 passed, 11 failed, 67 skipped (reduced from 98)
Backend coverage: 87.0% (exceeds 85% threshold)

.github/skills/utility-update-go-version-scripts/run.sh

@@ -0,0 +1,68 @@
+#!/usr/bin/env bash
+# Skill runner for utility-update-go-version
+# Updates local Go installation to match go.work requirements
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_ROOT="$(cd "$SCRIPT_DIR/../../.." && pwd)"
+
+GO_WORK_FILE="$PROJECT_ROOT/go.work"
+
+if [[ ! -f "$GO_WORK_FILE" ]]; then
+    echo "❌ go.work not found at $GO_WORK_FILE"
+    exit 1
+fi
+
+# Extract required Go version from go.work
+REQUIRED_VERSION=$(grep -E '^go [0-9]+\.[0-9]+(\.[0-9]+)?$' "$GO_WORK_FILE" | awk '{print $2}')
+
+if [[ -z "$REQUIRED_VERSION" ]]; then
+    echo "❌ Could not parse Go version from go.work"
+    exit 1
+fi
+
+echo "📋 Required Go version from go.work: $REQUIRED_VERSION"
+
+# Check current installed version
+CURRENT_VERSION=$(go version 2>/dev/null | grep -oE 'go[0-9]+\.[0-9]+(\.[0-9]+)?' | sed 's/go//' || echo "none")
+echo "📋 Currently installed Go version: $CURRENT_VERSION"
+
+if [[ "$CURRENT_VERSION" == "$REQUIRED_VERSION" ]]; then
+    echo "✅ Go version already matches requirement ($REQUIRED_VERSION)"
+    exit 0
+fi
+
+echo "🔄 Updating Go from $CURRENT_VERSION to $REQUIRED_VERSION..."
+
+# Download the new Go version using the official dl tool
+echo "📥 Downloading Go $REQUIRED_VERSION..."
+go install "golang.org/dl/go${REQUIRED_VERSION}@latest"
+
+# Download the SDK
+echo "📦 Installing Go $REQUIRED_VERSION SDK..."
+"go${REQUIRED_VERSION}" download
+
+# Update the system symlink
+SDK_PATH="$HOME/sdk/go${REQUIRED_VERSION}/bin/go"
+if [[ -f "$SDK_PATH" ]]; then
+    echo "🔗 Updating system Go symlink..."
+    sudo ln -sf "$SDK_PATH" /usr/local/go/bin/go
+else
+    echo "⚠️  SDK binary not found at expected path: $SDK_PATH"
+    echo "   You may need to add go${REQUIRED_VERSION} to your PATH manually"
+fi
+
+# Verify the update
+NEW_VERSION=$(go version 2>/dev/null | grep -oE 'go[0-9]+\.[0-9]+(\.[0-9]+)?' | sed 's/go//' || echo "unknown")
+echo ""
+echo "✅ Go updated successfully!"
+echo "   Previous: $CURRENT_VERSION"
+echo "   Current:  $NEW_VERSION"
+echo "   Required: $REQUIRED_VERSION"
+
+if [[ "$NEW_VERSION" != "$REQUIRED_VERSION" ]]; then
+    echo ""
+    echo "⚠️  Warning: Installed version ($NEW_VERSION) doesn't match required ($REQUIRED_VERSION)"
+    echo "   You may need to restart your terminal or IDE"
+fi