initial agent-mgr: app builder platform MVP

Go API server + Preact UI + Claude Code adapter.
- App-centric model (ideas, not repos)
- AgentProvider interface for multi-agent support
- K8s pod lifecycle for sandboxed agent sessions
- Gitea integration (create repos, push branches)
- WebSocket streaming for live session output
- Woodpecker CI/CD pipelines (kaniko build + kubectl deploy)

docker/Dockerfile

@@ -0,0 +1,23 @@
+# Stage 1: Build UI
+FROM node:22-slim AS ui-builder
+WORKDIR /ui
+COPY ui/package.json ui/package-lock.json* ./
+RUN npm ci --ignore-scripts
+COPY ui/ .
+RUN npm run build
+
+# Stage 2: Build Go binary
+FROM golang:1.23-alpine AS go-builder
+RUN apk add --no-cache git
+WORKDIR /src
+COPY go.mod go.sum ./
+RUN go mod download
+COPY . .
+COPY --from=ui-builder /ui/dist ./ui/dist
+RUN CGO_ENABLED=0 go build -o /agent-mgr ./cmd/agent-mgr
+
+# Stage 3: Runtime
+FROM gcr.io/distroless/static-debian12:nonroot
+COPY --from=go-builder /agent-mgr /agent-mgr
+EXPOSE 8080
+ENTRYPOINT ["/agent-mgr"]