feat: contact form backend for linux and freebsd servers

Assisted-by: GLM 5.3 Flash

justfile

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+# nuntius.
+#
+# Everything below the variable block is the standard recipe set from the `justfile`
+# skill, identical in every repository; project values live in the variable block only.
+binary := "nuntius"
+package := "./cmd/server"
+
+# What the test and bench recipes sweep. Scoped to the logic packages; the
+# thin cmd/ would drag the coverage total under the 80 percent floor. Keep
+# it equal to the Tests step in .gitea/workflows/test.yml.
+packages := "./internal/..."
+
+# The memory fence for the test recipes: a cgroup ceiling with swap off, so a
+# runaway run dies as a failed run and never eats the machine. 4G is the
+# default; the suite is small and quiet, so no raise is warranted.
+memlimit := "4G"
+
+bindir := env_var_or_default("BINDIR", env_var("HOME") / ".local" / "bin")
+
+default:
+    @just --list
+
+# Compile. Zero errors, zero warnings; -trimpath and -buildvcs make the binary place-independent and version-stamped.
+build:
+    CGO_ENABLED=0 go build -trimpath -buildvcs=true -ldflags "-s -w" -o bin/{{binary}} {{package}}
+
+# The test gate: the suite, no cache, the coverage floor, under the memory fence.
+test:
+    #!/usr/bin/env perl
+    my @fence = (q{systemd-run}, q{--user}, q{--scope},
+                 q{-p}, q{MemoryMax={{memlimit}}}, q{-p}, q{MemorySwapMax=0});
+    system(@fence, q{go}, q{test}, q{-count=1}, q{-timeout}, q{10m},
+      q{-coverprofile}, q{coverage.out}, qw({{packages}})) == 0
+      or die qq{the test suite failed\n};
+    open(my $c, q{-|}, q{go}, q{tool}, q{cover}, q{-func=coverage.out}) or die qq{cover: $!};
+    my $total;
+    while (my $l = <$c>) { $total = $1 if $l =~ m{^total:\s+\S+\s+([0-9.]+)%} }
+    close($c);
+    die qq{no total line in coverage.out\n} unless defined $total;
+    printf qq{Total coverage: %s%%\n}, $total;
+    exit($total < 80 ? 1 : 0);
+
+# The same suite under the race detector. The expensive one, still fenced.
+race:
+    systemd-run --user --scope -p MemoryMax={{memlimit}} -p MemorySwapMax=0 go test -race -count=1 -timeout 10m {{packages}}
+
+# Fast scoped run for iterating. This is the one that runs after every edit.
+unit pkgs=packages run=".*":
+    systemd-run --user --scope -p MemoryMax={{memlimit}} -p MemorySwapMax=0 go test {{pkgs}} -run '{{run}}'
+
+# Time-boxed fuzz of one target in one package. The package is required; never a gate.
+fuzz target pkg fuzztime="60s":
+    systemd-run --user --scope -p MemoryMax={{memlimit}} -p MemorySwapMax=0 go test -run '^$' -fuzz '{{target}}' -fuzztime={{fuzztime}} {{pkg}}
+
+# A ceiling would distort the measurement, and the recipe's own rule is that nothing else runs while it does.
+
+# Benchmarks. On an idle machine only, and deliberately unfenced.
+bench pkgs=packages:
+    go test -run '^$' -bench=. -benchmem -count=5 {{pkgs}}
+
+# Format in place.
+fmt:
+    gofmt -w .
+
+# Zero diff. Prints nothing when everything is formatted.
+fmt-check:
+    #!/usr/bin/env perl
+    open(my $g, q{-|}, q{gofmt}, q{-l}, q{.}) or die qq{gofmt: $!};
+    my @bad = <$g>;
+    close($g);
+    print @bad;
+    exit(@bad ? 1 : 0);
+
+# Both static gates: go vet and go fix -diff.
+vet:
+    go vet ./...
+    go fix -diff ./...
+
+# The definition of done, in one command. Once per task, never per edit.
+gates: build fmt-check vet test race
+
+# Build artefacts only, not the installed binary.
+clean:
+    rm -rf bin/ coverage.out
+
+# Build, then copy the binary into bindir.
+install: build
+    install -d "{{bindir}}"
+    install -m 755 bin/{{binary}} "{{bindir}}/{{binary}}"
+
+# Remove the installed binary.
+uninstall:
+    rm -f "{{bindir}}/{{binary}}"
+
+# Run the program. The flag is there because `go run` does not stamp the build otherwise.
+run:
+    go run -buildvcs=true {{package}}
+
+# Run with watch or hot reload, where the project has one.
+dev:
+    go run -buildvcs=true {{package}}
+
+# Coverage report as an HTML map from the gate's profile; not standard because the gate needs only the numeric floor, and a browser artefact is exploration, not a gate.
+coverage-html: test
+    go tool cover -html=coverage.out -o coverage.html