feat: Add devcontainer configuration for n8n-workflows development

- Configure Claude Code optimized devcontainer with Python support
- Add Python development tools (black, flake8, isort) to Dockerfile
- Include VS Code extensions for Python and workflow development
- Add firewall script for secure development environment
- Update .gitignore to exclude Claude Code local settings

🤖 Generated with [Claude Code](https://claude.ai/code)

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

.devcontainer/init-firewall.sh

@@ -0,0 +1,118 @@
+#!/bin/bash
+set -euo pipefail  # Exit on error, undefined vars, and pipeline failures
+IFS=$'\n\t'       # Stricter word splitting
+
+# Flush existing rules and delete existing ipsets
+iptables -F
+iptables -X
+iptables -t nat -F
+iptables -t nat -X
+iptables -t mangle -F
+iptables -t mangle -X
+ipset destroy allowed-domains 2>/dev/null || true
+
+# First allow DNS and localhost before any restrictions
+# Allow outbound DNS
+iptables -A OUTPUT -p udp --dport 53 -j ACCEPT
+# Allow inbound DNS responses
+iptables -A INPUT -p udp --sport 53 -j ACCEPT
+# Allow outbound SSH
+iptables -A OUTPUT -p tcp --dport 22 -j ACCEPT
+# Allow inbound SSH responses
+iptables -A INPUT -p tcp --sport 22 -m state --state ESTABLISHED -j ACCEPT
+# Allow localhost
+iptables -A INPUT -i lo -j ACCEPT
+iptables -A OUTPUT -o lo -j ACCEPT
+
+# Create ipset with CIDR support
+ipset create allowed-domains hash:net
+
+# Fetch GitHub meta information and aggregate + add their IP ranges
+echo "Fetching GitHub IP ranges..."
+gh_ranges=$(curl -s https://api.github.com/meta)
+if [ -z "$gh_ranges" ]; then
+    echo "ERROR: Failed to fetch GitHub IP ranges"
+    exit 1
+fi
+
+if ! echo "$gh_ranges" | jq -e '.web and .api and .git' >/dev/null; then
+    echo "ERROR: GitHub API response missing required fields"
+    exit 1
+fi
+
+echo "Processing GitHub IPs..."
+while read -r cidr; do
+    if [[ ! "$cidr" =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}/[0-9]{1,2}$ ]]; then
+        echo "ERROR: Invalid CIDR range from GitHub meta: $cidr"
+        exit 1
+    fi
+    echo "Adding GitHub range $cidr"
+    ipset add allowed-domains "$cidr"
+done < <(echo "$gh_ranges" | jq -r '(.web + .api + .git)[]' | aggregate -q)
+
+# Resolve and add other allowed domains
+for domain in \
+    "registry.npmjs.org" \
+    "api.anthropic.com" \
+    "sentry.io" \
+    "statsig.anthropic.com" \
+    "statsig.com"; do
+    echo "Resolving $domain..."
+    ips=$(dig +short A "$domain")
+    if [ -z "$ips" ]; then
+        echo "ERROR: Failed to resolve $domain"
+        exit 1
+    fi
+    
+    while read -r ip; do
+        if [[ ! "$ip" =~ ^[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}$ ]]; then
+            echo "ERROR: Invalid IP from DNS for $domain: $ip"
+            exit 1
+        fi
+        echo "Adding $ip for $domain"
+        ipset add allowed-domains "$ip"
+    done < <(echo "$ips")
+done
+
+# Get host IP from default route
+HOST_IP=$(ip route | grep default | cut -d" " -f3)
+if [ -z "$HOST_IP" ]; then
+    echo "ERROR: Failed to detect host IP"
+    exit 1
+fi
+
+HOST_NETWORK=$(echo "$HOST_IP" | sed "s/\.[0-9]*$/.0\/24/")
+echo "Host network detected as: $HOST_NETWORK"
+
+# Set up remaining iptables rules
+iptables -A INPUT -s "$HOST_NETWORK" -j ACCEPT
+iptables -A OUTPUT -d "$HOST_NETWORK" -j ACCEPT
+
+# Set default policies to DROP first
+iptables -P INPUT DROP
+iptables -P FORWARD DROP
+iptables -P OUTPUT DROP
+
+# First allow established connections for already approved traffic
+iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
+iptables -A OUTPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
+
+# Then allow only specific outbound traffic to allowed domains
+iptables -A OUTPUT -m set --match-set allowed-domains dst -j ACCEPT
+
+echo "Firewall configuration complete"
+echo "Verifying firewall rules..."
+if curl --connect-timeout 5 https://example.com >/dev/null 2>&1; then
+    echo "ERROR: Firewall verification failed - was able to reach https://example.com"
+    exit 1
+else
+    echo "Firewall verification passed - unable to reach https://example.com as expected"
+fi
+
+# Verify GitHub API access
+if ! curl --connect-timeout 5 https://api.github.com/zen >/dev/null 2>&1; then
+    echo "ERROR: Firewall verification failed - unable to reach https://api.github.com"
+    exit 1
+else
+    echo "Firewall verification passed - able to reach https://api.github.com as expected"
+fi