Add coverage reporting/badges and split CI between Gitea and GitHub (#5)

Merge dotnet+jest coverage via reportgenerator, publish a self-hosted
coverage badge and build-status badges on the readme. Gitea remains the
full pipeline (build/test/docker push/deploy-qa/smoke); GitHub only
builds and tests since it has no registry secrets or qa runner.

Reviewed-on: #5

scripts/ci/coverage.sh

@@ -0,0 +1,32 @@
+#!/usr/bin/env bash
+# Merges the .NET (coverlet/Cobertura) and admin (Jest/lcov) coverage output
+# produced by test.sh into one report via reportgenerator, prints a summary,
+# appends a build-report summary when running under Actions, and refreshes
+# the coverage badge committed at badges/coverage.svg. Readme embeds that
+# badge via a relative path, which resolves on both GitHub and Gitea since
+# the same repo content is pushed to both remotes.
+set -euo pipefail
+cd "$(dirname "${BASH_SOURCE[0]}")" && source ./lib.sh
+cd "$CI_ROOT"
+
+ensure_dotnet
+ensure_reportgenerator
+
+REPORT_DIR="$CI_ROOT/coverage/report"
+
+log "Merging coverage reports with reportgenerator"
+reportgenerator \
+  -reports:"coverage/dotnet/**/coverage.cobertura.xml;src/admin/coverage/lcov.info" \
+  -targetdir:"$REPORT_DIR" \
+  -reporttypes:"Badges;MarkdownSummaryGithub;TextSummary"
+
+cat "$REPORT_DIR/Summary.txt"
+
+if [[ -n "${GITHUB_STEP_SUMMARY:-}" ]]; then
+  cat "$REPORT_DIR/SummaryGithub.md" >> "$GITHUB_STEP_SUMMARY"
+fi
+
+mkdir -p "$CI_ROOT/badges"
+cp "$REPORT_DIR/badge_linecoverage.svg" "$CI_ROOT/badges/coverage.svg"
+
+log "coverage.sh complete"