chore: dev environment — signet testnet stack, mock LND RPCs, faucet button

Switch docker-compose from regtest to signet, add standalone testnet stack
(docker-compose.testnet.yml) with Bitcoin+LND+ThunderHub+Fedimint. Mock
backend now auto-detects Podman/Docker sockets and includes full LND/Lightning
RPC mocks. Dev scripts refactored with boot mode, testnet option, and macOS
EAGAIN fix for port cleanup. Added dev faucet button to Home.vue.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

neode-ui/start-dev.sh

@@ -25,12 +25,16 @@ check_port() {
     lsof -ti:$1 > /dev/null 2>&1
 }
 
-# Function to kill process on a port
+# Function to kill process on a port (avoids xargs which causes EAGAIN on macOS)
 kill_port() {
     local port=$1
-    if check_port $port; then
-        echo -e "${YELLOW}⚠️  Port $port is in use, cleaning up...${NC}"
-        lsof -ti:$port | xargs kill -9 2>/dev/null || true
+    local pids
+    pids=$(lsof -ti:"$port" 2>/dev/null) || true
+    if [ -n "$pids" ]; then
+        echo -e "${YELLOW}  Port $port in use, cleaning up...${NC}"
+        echo "$pids" | while read -r pid; do
+            kill -9 "$pid" 2>/dev/null || true
+        done
         sleep 1
     fi
 }
@@ -85,7 +89,5 @@ echo -e "${BLUE}🚀 Starting servers...${NC}"
 echo ""
 
 # Use npm run dev:mock (includes AIUI dev server automatically)
-npm run dev:mock
-
-# Note: The script will stay running until Ctrl+C
+exec npm run dev:mock