Fix issue templates referencing a nonexistent label

.github/ISSUE_TEMPLATE/add-backend.md

@@ -2,7 +2,7 @@
 name: Add a backend / adapter
 about: Propose or document support for a new routable backend
 title: "[backend] "
-labels: feature, backend
+labels: enhancement, backend
 ---
 
 Adding a backend is usually a **config edit, not a code change** — a new roster entry, not new

.github/ISSUE_TEMPLATE/feature.md

@@ -2,7 +2,7 @@
 name: Feature request
 about: Suggest a new capability or improvement
 title: "[feature] "
-labels: feature
+labels: enhancement
 ---
 
 ## Problem / motivation

CHANGELOG.md

@@ -7,6 +7,14 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Internal
+
+- **Issue templates now declare labels that exist.** `feature.md` and `add-backend.md` asked for a
+  `feature` label the repo has never had, so `gh issue create` failed outright on it and
+  UI-filed issues landed unlabeled. Both now use `enhancement`; the `backend` label
+  `add-backend.md` also referenced has been created. Every label named across the three
+  templates now resolves.
+
 ## [0.20.1] - 2026-08-01
 
 ### Fixed