Port ntfy to locally built container image (#202)

## Summary
- Add `containers/ntfy/Dockerfile` — three-stage build (Node web UI, Go+CGO server, Alpine runtime) pinned to commit SHA `a03a37fe` (v2.17.0), sourced from forge mirror
- Update ntfy deployment image from `binwiederhier/ntfy:v2.17.0` to `registry.ops.eblu.me/blumeops/ntfy:v1.0.0`
- Note fish shell in CLAUDE.md

## Deployment
After merge, release the container image:
```fish
mise run container-tag-and-release ntfy v1.0.0
```
Then sync:
```fish
argocd app sync ntfy
```

## Test plan
- [x] `docker build` succeeds
- [x] `dagger call build --src=. --container-name=ntfy` succeeds (exit 0, container ID printed)
- [x] `ntfy --help` works in built container
- [ ] Tag and release `ntfy-v1.0.0` after merge
- [ ] Verify ntfy pod starts with new image
- [ ] Verify health endpoint responds at `ntfy.ops.eblu.me/v1/health`

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

Reviewed-on: https://forge.ops.eblu.me/eblume/blumeops/pulls/202

containers/ntfy/Dockerfile

@@ -0,0 +1,62 @@
+# ntfy push notification server
+# Three-stage build: Web UI (Node), server (Go+SQLite), runtime (Alpine)
+
+ARG NTFY_VERSION=v2.17.0
+ARG NTFY_COMMIT=a03a37feb1869e84e3af0dd6190bdc7183f211ec
+
+FROM node:22-alpine AS web-build
+
+ARG NTFY_COMMIT
+RUN apk add --no-cache git
+
+RUN mkdir /app && cd /app \
+    && git init \
+    && git remote add origin https://forge.ops.eblu.me/eblume/ntfy.git \
+    && git fetch --depth 1 origin ${NTFY_COMMIT} \
+    && git checkout FETCH_HEAD
+
+WORKDIR /app/web
+RUN npm ci
+RUN npm run build
+
+FROM golang:alpine3.22 AS build
+
+ARG NTFY_VERSION
+ARG NTFY_COMMIT
+RUN apk add --no-cache build-base git
+
+RUN mkdir /app && cd /app \
+    && git init \
+    && git remote add origin https://forge.ops.eblu.me/eblume/ntfy.git \
+    && git fetch --depth 1 origin ${NTFY_COMMIT} \
+    && git checkout FETCH_HEAD
+
+WORKDIR /app
+
+# Copy pre-built web UI assets
+COPY --from=web-build /app/web/build /app/server/site
+
+# Create docs placeholder with dummy file (go:embed requires non-empty dir)
+RUN mkdir -p server/docs && touch server/docs/placeholder
+
+ENV CGO_ENABLED=1
+
+RUN go build \
+    -o /ntfy \
+    -tags sqlite_omit_load_extension,osusergo,netgo \
+    -ldflags "-linkmode=external -extldflags=-static -s -w -X main.version=${NTFY_VERSION}"
+
+FROM alpine:3.22
+
+LABEL org.opencontainers.image.title=ntfy
+LABEL org.opencontainers.image.description="ntfy is a simple HTTP-based pub-sub notification service"
+LABEL org.opencontainers.image.source=https://github.com/binwiederhier/ntfy
+
+RUN apk --no-cache add tzdata
+
+COPY --from=build /ntfy /usr/bin/ntfy
+
+EXPOSE 80
+
+USER 65534
+ENTRYPOINT ["/usr/bin/ntfy"]