feat(ingestion): add Dockerfile and extend CD to build+push ingestion image

Ingestion server is a pure-Go HTTP binary — alpine runtime, no node.js.
CD now builds both supervisor and ingestion images on every push,
updates both deployment.yaml files in the infra repo.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ingestion/Dockerfile

@@ -0,0 +1,34 @@
+# syntax=docker/dockerfile:1
+
+FROM golang:1.26-bookworm AS builder
+
+ARG VERSION=dev
+WORKDIR /src
+
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY . .
+RUN CGO_ENABLED=0 GOOS=linux GOARCH=amd64 \
+    go build -trimpath -ldflags="-s -w" \
+    -o /out/ingestion ./cmd/server
+
+FROM alpine:3.21
+
+COPY --from=builder /out/ingestion /usr/local/bin/ingestion
+
+RUN addgroup -S ingestion && adduser -S -G ingestion ingestion
+
+WORKDIR /app
+
+# brain/ is writable state — mount a PersistentVolume here
+VOLUME /app/brain
+
+ENV INGEST_BRAIN_DIR=/app/brain
+ENV INGEST_PORT=3300
+
+USER ingestion
+
+EXPOSE 3300
+
+ENTRYPOINT ["/usr/local/bin/ingestion"]