Initial commit: PRD, build tooling, and design mockups

Foodster is a self-hosted dinner log and meal suggester for one household.
Stage 1 (eating history) is in development; stage 2 (the suggester) follows
once there is enough history to weight against.

Replace the PRD's original stack (Nuxt, Postgres, Drizzle, Pico CSS) with
Go 1.27, net/http, templ, Datastar and SQLite — one static binary, no
Node.js in the build. Sections 3, 4, 5, 9, 10 and 11 are rewritten to match.

Record the decisions made while reviewing mockups:

- the UI is written in Finnish; PRD, code and comments stay English
- access is one shared password over HTTP Basic rather than open on the LAN
- images are CalVer vYYYYMMDD-N, built with Podman, run under Docker Compose
- registry coordinates live in .env, so no infrastructure detail is
  committed and the MIT publication option stays open

mockups/ holds standalone HTML design studies. log-fi.html is the current
one; the others are superseded exploration kept for reference.

Containerfile

@@ -0,0 +1,25 @@
+# syntax=docker/dockerfile:1
+
+FROM golang:1.27-alpine AS build
+WORKDIR /src
+
+COPY go.mod go.sum ./
+RUN go mod download
+
+COPY . .
+
+ARG VERSION=dev
+RUN go tool templ generate && \
+    CGO_ENABLED=0 GOOS=linux go build \
+      -trimpath \
+      -ldflags="-s -w -X main.version=${VERSION}" \
+      -o /foodster ./cmd/foodster
+
+# Nothing but the binary. modernc.org/sqlite is pure Go, so there is no libc
+# to carry along, and time/tzdata is compiled in because scratch has no
+# zoneinfo.
+FROM scratch
+COPY --from=build /foodster /foodster
+USER 65534:65534
+EXPOSE 8080
+ENTRYPOINT ["/foodster"]