Add Coolify deployment support

Multi-stage Dockerfile builds the email-builder, admin frontend, and Go
backend from source and stuffs assets into the binary. The runtime-only
image moved to Dockerfile.goreleaser for release builds. Adds a Coolify
compose file with magic service variables, healthchecks, and volumes.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Dockerfile

@@ -1,3 +1,50 @@
+# Self-contained build for EagleCast. Builds the email-builder and admin
+# frontend, compiles the Go backend, and stuffs all static assets into a
+# single binary. Used by PaaS platforms like Coolify that build from git.
+# (Release builds via goreleaser use Dockerfile.goreleaser instead.)
+
+ARG APP_VERSION=v1.0.0
+
+# ---- email-builder (React) ----
+FROM node:22-alpine AS email-builder
+WORKDIR /build/email-builder
+COPY frontend/email-builder/package.json frontend/email-builder/yarn.lock ./
+RUN yarn install --frozen-lockfile
+COPY frontend/email-builder/ ./
+RUN yarn build
+
+# ---- admin frontend (Vue) ----
+FROM node:22-alpine AS frontend
+ARG APP_VERSION
+WORKDIR /build/frontend
+COPY frontend/package.json frontend/yarn.lock ./
+RUN yarn install --frozen-lockfile
+COPY frontend/ ./
+COPY --from=email-builder /build/email-builder/dist ./public/static/email-builder
+ENV VUE_APP_VERSION=${APP_VERSION}
+RUN yarn build
+
+# ---- backend (Go) ----
+FROM golang:1.26-alpine AS backend
+ARG APP_VERSION
+WORKDIR /build
+COPY go.mod go.sum ./
+RUN go mod download
+RUN go install github.com/knadh/stuffbin/...@latest
+COPY . .
+COPY --from=frontend /build/frontend/dist ./frontend/dist
+RUN CGO_ENABLED=0 go build -o eaglecast \
+    -ldflags="-s -w -X 'main.buildString=${APP_VERSION} (docker)' -X 'main.versionString=${APP_VERSION}'" \
+    ./cmd
+RUN /go/bin/stuffbin -a stuff -in eaglecast -out eaglecast \
+    config.toml.sample \
+    schema.sql queries:/queries permissions.json \
+    static/public:/public \
+    static/email-templates \
+    frontend/dist:/admin \
+    i18n:/i18n
+
+# ---- runtime ----
 FROM alpine:latest
 
 # Install dependencies
@@ -7,7 +54,7 @@ RUN apk --no-cache add ca-certificates tzdata shadow su-exec
 WORKDIR /eaglecast
 
 # Copy only the necessary files
-COPY eaglecast .
+COPY --from=backend /build/eaglecast .
 COPY config.toml.sample config.toml
 
 # Copy the entrypoint script