Pull all fallback base images from Harbor, not Docker Hub

Every language's Dockerfile fallback template now pulls from
harbor.192.168.1.7.nip.io/base-images/... (mirrored from Docker Hub via
the new devops-base-images repo) instead of pulling live from Docker
Hub on every build. Eliminates that external dependency at build time,
and lets the mirrored tags be deliberately the leanest official
variant rather than whatever a public tag happens to default to.

- go: unchanged tags (golang:1.22-alpine, alpine:3.20 — already
  minimal), just re-hosted.
- node/python/java: moved from their Debian-slim defaults to the
  -alpine equivalent (node:20-alpine, python:3.12-alpine,
  maven:3-eclipse-temurin-21-alpine, eclipse-temurin:21-jre-alpine).
- php: bigger change — dropped php:*-apache (Debian, full Apache
  httpd) entirely for php:*-cli-alpine + PHP's own built-in dev server
  (`php -S`), moving to port 8080 like every other language instead of
  PHP's special-cased 80. Not production-grade PHP serving (PHP's own
  docs call the built-in server not designed for that), but genuinely
  minimal and fine for a homelab/demo app — would need php-fpm+nginx
  for anything serving real traffic.

Only versions actually mirrored into Harbor resolve now — a
dockerBuildVersion whose tag isn't in devops-base-images/images.txt
needs that added and re-mirrored first, unlike pulling straight from
Docker Hub where any tag "just worked". Chose keeping a shell (Alpine)
over full distroless — homelab kubectl-exec debuggability weighed more
than the last bit of attack-surface reduction.

resources/com/homelab/go-Dockerfile

@@ -4,14 +4,23 @@
 # kafka-specific CGO toggle. Assumes a standard single-binary repo layout
 # (main package at the repo root) — a repo with a different structure
 # should just bring its own Dockerfile, same as demo-go-app does.
-FROM golang:${version}-alpine AS build
+# Both stages pulled from Harbor's base-images project (mirrored from
+# Docker Hub via devops-base-images), not Docker Hub directly — see that
+# repo's README for the one-off mirror setup and why (build-time
+# dependency on an external registry, plus wanting to pick the leanest
+# variant of each deliberately rather than accept whatever a public tag
+# defaults to). Only versions actually mirrored there resolve — passing
+# a dockerBuildVersion whose tag isn't in devops-base-images/images.txt
+# yet needs that added and re-mirrored first, unlike pulling straight
+# from Docker Hub where any tag "just worked".
+FROM harbor.192.168.1.7.nip.io/base-images/golang:${version}-alpine AS build
 WORKDIR /src
 COPY go.mod go.sum* ./
 RUN go mod download 2>/dev/null || true
 COPY . .
 RUN CGO_ENABLED=0 go build -o /app .
 
-FROM alpine:3.20
+FROM harbor.192.168.1.7.nip.io/base-images/alpine:3.20
 COPY --from=build /app /app
 EXPOSE 8080
 ENTRYPOINT ["/app"]