feat: scaffold agentmon services and k8s deploy

Adds Go microservices (ingest-gateway, event-processor, query-api, web-ui), NATS+Postgres wiring, initial schema/init job, ingress manifests for LAN+tailnet, and a multi-arch image build script.

build/build-images.sh

@@ -0,0 +1,32 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Builds multi-arch images by default.
+#
+# Defaults:
+# - PLATFORM="linux/amd64,linux/arm64"
+# - PUSH_ARGS="--push" (set to --load for a single-arch local build)
+
+REGISTRY=${REGISTRY:-"gitea-http.taildb3494.ts.net/will/agentmon"}
+TAG=${TAG:-"dev-20260117-0832"}
+PLATFORM=${PLATFORM:-"linux/amd64,linux/arm64"}
+
+services=(
+  ingest-gateway
+  event-processor
+  query-api
+  web-ui
+)
+
+for svc in "${services[@]}"; do
+  image="${REGISTRY}/${svc}:${TAG}"
+
+  echo "==> Building ${image} (${PLATFORM})"
+  docker buildx build \
+    --platform "${PLATFORM}" \
+    --build-arg CMD="${svc}" \
+    -f build/dockerfiles/Dockerfile \
+    -t "${image}" \
+    ${PUSH_ARGS:-"--push"} \
+    .
+done