test(smoke): add smoke tests and coverage gate for backend

Signed-off-by: Noooste <83548733+Noooste@users.noreply.github.com>

scripts/coverage-gate.sh

@@ -0,0 +1,86 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Usage: scripts/coverage-gate.sh <coverage.out>
+#
+# Enforces:
+#   - Total backend coverage >= 70% (excluding backend/main.go and backend/docs/).
+#   - Per-package floor >= 70% for each of:
+#       internal/auth, internal/config, internal/handlers, internal/services.
+
+if [ "$#" -ne 1 ]; then
+    echo "usage: $0 <coverage.out>" >&2
+    exit 2
+fi
+
+COVERAGE_IN="$1"
+TOTAL_FLOOR="70.0"
+PER_PKG_FLOOR="70.0"
+PER_PKG_GATES=(
+    "internal/auth"
+    "internal/config"
+    "internal/handlers"
+    "internal/services"
+)
+
+if [ ! -f "$COVERAGE_IN" ]; then
+    echo "error: coverage file not found: $COVERAGE_IN" >&2
+    exit 2
+fi
+
+FILTERED="coverage-filtered.out"
+trap 'rm -f "$FILTERED"' EXIT
+
+# Keep the mode: line, drop excluded paths.
+# Excluded from coverage totals:
+#   - main.go: entry point, covered transitively by smoke.
+#   - backend/docs/: generated swagger.
+#   - mocks/ and *_mock.go: test infrastructure, not production code.
+#   - services/s3.go: network methods deferred to smoke per parent spec
+#     (docs/superpowers/specs/2026-04-17-backend-test-suite-design.md §internal/services).
+grep -E '^(mode:|.*/)' "$COVERAGE_IN" \
+    | grep -v '/main\.go' \
+    | grep -v '/docs/' \
+    | grep -v '/mocks/' \
+    | grep -v '_mock\.go' \
+    | grep -v '/services/s3\.go' \
+    > "$FILTERED"
+
+FUNC_OUT=$(cd backend && go tool cover -func="../$FILTERED")
+TOTAL_PCT=$(echo "$FUNC_OUT" | awk '/^total:/ {gsub("%",""); print $NF}')
+
+if [ -z "$TOTAL_PCT" ]; then
+    echo "error: could not parse total coverage from go tool cover output" >&2
+    echo "$FUNC_OUT" >&2
+    exit 2
+fi
+
+echo "== Coverage summary =="
+printf "  %-30s %s%%\n" "total" "$TOTAL_PCT"
+
+FAIL=0
+if awk -v a="$TOTAL_PCT" -v b="$TOTAL_FLOOR" 'BEGIN { exit !(a+0 < b+0) }'; then
+    echo "FAIL total: ${TOTAL_PCT}% < ${TOTAL_FLOOR}%"
+    FAIL=1
+fi
+
+for pkg in "${PER_PKG_GATES[@]}"; do
+    pkg_pct=$(echo "$FUNC_OUT" \
+        | awk -v p="/$pkg/" '$1 ~ p { sub("%","",$NF); sum+=$NF; n++ } END { if (n>0) printf "%.1f", sum/n; else print "n/a" }')
+    printf "  %-30s %s%%\n" "$pkg" "$pkg_pct"
+    if [ "$pkg_pct" = "n/a" ]; then
+        echo "FAIL $pkg: no coverage data"
+        FAIL=1
+        continue
+    fi
+    if awk -v a="$pkg_pct" -v b="$PER_PKG_FLOOR" 'BEGIN { exit !(a+0 < b+0) }'; then
+        echo "FAIL $pkg: ${pkg_pct}% < ${PER_PKG_FLOOR}%"
+        FAIL=1
+    fi
+done
+
+if [ "$FAIL" -ne 0 ]; then
+    exit 1
+fi
+
+echo "PASS"