docs/chore: Phase 1 doc/code hygiene (code-review.md § Phase 1)

Removes ~30 stale "Phase N" / historical-staging comment references from
code and shell scripts now that v1.0 is done; fixes a stale dashboard
comment claiming applications/send-log were unimplemented; adds a CSRF ADR
to security.md documenting the Origin-check-over-tokens decision; resolves
docs/logo in roadmap.md (directory doesn't exist, criterion already met);
adds a gofmt -l check to CI so unformatted Go fails the build.

The known-limitations write-up for the log-tailer offset gap (the other
Phase 1 item) was already present in architecture.md § Log tailer, so no
change was needed there.

gofmt/go vet/go test clean on both Go modules (main + test/e2e), verified
on the dev server.

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

build/Dockerfile

@@ -13,8 +13,7 @@ WORKDIR /src
 # Version stamped into both binaries; MUST match the image tag (spec 7.5.A).
 ARG VERSION=dev
 
-# Module metadata first for layer caching. go.sum arrived in Phase 2 with the
-# SQLite driver and bcrypt.
+# Module metadata first for layer caching.
 COPY go.mod go.sum ./
 RUN go mod download
 
@@ -36,7 +35,7 @@ FROM debian:bookworm-slim AS runtime
 ENV DEBIAN_FRONTEND=noninteractive
 
 # Preseed Postfix so its install is non-interactive and yields a working
-# main.cf. The real relay configuration is generated by the panel in Phase 5.
+# main.cf. The real relay configuration is generated by the panel.
 RUN echo "postfix postfix/mailname string localhost" | debconf-set-selections \
  && echo "postfix postfix/main_mailer_type string Internet Site" | debconf-set-selections \
  && apt-get update \