fix: resolve cache eviction lock-up and migrate telemetry [patch-release]

universal_cache: stop the write-lock convoy / 100%-CPU spin (observed via pprof: one ServeHTTP goroutine holding c.mu.Lock for hours while 119 requests queued). The per-request populate path (updateLocalCache) PushFronted a duplicate LRU node + overwrote items[key] without removing the prior node; once eviction deleted the key, orphan nodes at Back() were never removable and the eviction loop spun forever under the write lock. Replace the entry in place (mirroring setLocal) and harden evictOldest with a forward-progress guard. Adds universal_cache_orphan_test.go.

telemetry: delete the hand-rolled client; call oss-telemetry v0.2.3 (vendored, Yaegi-safe) directly from New(), once per process via sync.Once.

version: add version.go + workflow-prepare.sh so the release semver is stamped into source at build time (the value cannot be resolved at runtime under Yaegi). dev/source builds keep the 0.0.0-dev sentinel and emit no telemetry.

workflow-prepare.sh

@@ -0,0 +1,67 @@
+#!/usr/bin/env bash
+#
+# workflow-prepare.sh — stamp the release version into version.go at build time.
+#
+# The shared go-release workflow (lukaszraczylo/shared-actions go-release.yaml)
+# runs this script, if present, from the repository root BEFORE GoReleaser
+# builds and tags. Traefik runs this plugin under Yaegi, where the version
+# cannot be resolved from build info at runtime, so the released semver must be
+# baked into source here.
+#
+# Version source — first non-empty wins:
+#   $VERSION  $VERSION_TAG  $SEMVER  $NEW_VERSION  $RELEASE_VERSION
+# A leading "v"/"V" is stripped.
+#
+# NOTE: go-release.yaml @main does not yet pass the computed version into this
+# step's environment. Add it to the "Run workflow prepare script" step, e.g.:
+#   env:
+#     VERSION: ${{ needs.version.outputs.version }}   # bare, no leading v
+#
+# The shared workflow runs this script in its test, version AND release jobs,
+# but only the release job has a computed version. So a missing version is a
+# no-op (leave the dev sentinel) — NOT a hard failure, otherwise the test/version
+# jobs would break. A malformed version that IS provided is a hard error. Wire
+# the env only on the release job's prepare step (see header note above).
+set -euo pipefail
+
+FILE="version.go"
+CONST="traefikoidcPluginVersion"
+
+VER="${VERSION:-${VERSION_TAG:-${SEMVER:-${NEW_VERSION:-${RELEASE_VERSION:-}}}}}"
+VER="${VER#v}"
+VER="${VER#V}"
+
+if [ -z "$VER" ]; then
+  if [ "${GITHUB_ACTIONS:-}" = "true" ]; then
+    echo "workflow-prepare: WARNING no version provided; leaving ${FILE} at the dev placeholder. If this is the release build, set 'env: VERSION: \${{ needs.version.outputs.version }}' on the release job's prepare step — otherwise the release ships 0.0.0-dev and emits no telemetry." >&2
+  else
+    echo "workflow-prepare: no version provided; leaving dev placeholder in ${FILE} (local build)"
+  fi
+  exit 0
+fi
+
+# Accept MAJOR[.MINOR[.PATCH]] with optional -prerelease / +build (semver-ish,
+# matching the oss-telemetry receiver's validator).
+if ! printf '%s' "$VER" | grep -Eq '^[0-9]+(\.[0-9]+){0,2}(-[0-9A-Za-z.-]+)?(\+[0-9A-Za-z.-]+)?$'; then
+  echo "workflow-prepare: ERROR version '${VER}' is not semver-shaped" >&2
+  exit 1
+fi
+
+if [ ! -f "$FILE" ]; then
+  echo "workflow-prepare: ERROR ${FILE} not found (run from repository root)" >&2
+  exit 1
+fi
+
+# Rewrite only the value of ${CONST}, anchored on the constant name so the
+# sibling devPluginVersion sentinel is left untouched.
+tmp="$(mktemp)"
+sed -E "s/(${CONST}[[:space:]]*=[[:space:]]*\")[^\"]*(\")/\1${VER}\2/" "$FILE" > "$tmp"
+mv "$tmp" "$FILE"
+
+if ! grep -Eq "${CONST}[[:space:]]*=[[:space:]]*\"${VER}\"" "$FILE"; then
+  echo "workflow-prepare: ERROR failed to stamp version into ${FILE}" >&2
+  exit 1
+fi
+
+command -v gofmt >/dev/null 2>&1 && gofmt -w "$FILE"
+echo "workflow-prepare: stamped ${CONST} = \"${VER}\" in ${FILE}"