Add Dockerfile, fix SQLite immutable mode, URL-encode credentials

- Dockerfile: multi-stage build with golang:1.26 and alpine + ffmpeg
- SQLite: use file: URI with immutable=1 for read-only access
- URL builder: encode user/pass with PathEscape/QueryEscape for
  special characters (@, \, :, etc.)
- Health endpoint: truncate uptime to seconds
- Release skill: update smoke test to /api endpoint
- Remove unused ValidateID function

Dockerfile

@@ -0,0 +1,28 @@
+FROM golang:1.26-alpine AS builder
+
+RUN apk add --no-cache gcc musl-dev
+
+WORKDIR /src
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY . .
+
+ARG VERSION=dev
+RUN CGO_ENABLED=1 go build -ldflags "-s -w -X main.version=${VERSION}" -o /strix .
+
+FROM alpine:latest
+
+RUN apk add --no-cache ffmpeg ca-certificates
+
+COPY --from=builder /strix /usr/local/bin/strix
+
+WORKDIR /app
+COPY cameras.db .
+
+EXPOSE 4567
+
+HEALTHCHECK --interval=30s --timeout=3s CMD wget -q --spider http://localhost:4567/api/health || exit 1
+
+USER nobody
+ENTRYPOINT ["strix"]