Server: rewrite in Go as an API-only service

Same endpoints, request formats, validation rules and InfluxDB layout as
the Next.js server, so the car needs no change: POST /v1/telemetry,
PUT /v1/consumption/daily, PUT /v1/charging-sessions/{id}, GET
/v1/consumption/history/{id}, GET /v1/health. The dashboard, login and
the /v1/history reads are gone; Grafana takes over the dashboards.

- Go 1.26 standard library (net/http routing, log/slog) plus the
  official InfluxDB 2 client. Fails closed at startup on a missing
  InfluxDB setting or an ingest token under 24 characters.
- ABRP forwarder ported: newest fresh sample, rate limited, never
  queued, credentials only in the form body.
- 22 tests: validation, aggregation, forwarding, config, and the
  handlers through a fake store. govulncheck clean (x/net 0.60.0,
  toolchain go1.26.9).
- Image: static binary on distroless, about 11 MB, UID 65532, port
  8080; the build runs vet and the tests.
- Dev shell: Go, gopls and govulncheck instead of Node.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QLJfZQZeAKAwSqViTmLzki

server/Dockerfile

@@ -0,0 +1,16 @@
+# The car server: one static Go binary on distroless, running as non-root.
+# Configuration comes from the environment at runtime; nothing secret is baked in.
+
+FROM docker.io/library/golang:1.26.9-alpine AS build
+WORKDIR /src
+ENV CGO_ENABLED=0 GOFLAGS=-trimpath GOTOOLCHAIN=local
+COPY go.mod go.sum ./
+RUN go mod download && go mod verify
+COPY *.go ./
+RUN go vet ./... && go test ./... && go build -ldflags="-s -w" -o /out/server .
+
+FROM gcr.io/distroless/static-debian12:nonroot
+COPY --from=build /out/server /server
+USER 65532:65532
+EXPOSE 8080
+ENTRYPOINT ["/server"]