feat: refresh a single repository from its own button (#2)

* feat(refresh): refresh a single repository with POST /refresh?repo=

The endpoint refreshes one configured repository and returns the full state plus the repo name.
Each repository has a 60-second cooldown that is separate from the full-refresh limit.
A running full refresh or a refresh of the same repository returns 409.
An unknown repository returns 404. Cross-site and disabled-config behaviour stay the same.
The collector reuses its fetch path and replaces only that repository.

* feat(ui): add a refresh button beside each repository

The button appears in the project list and in each attention group header.
It stays hidden when the server disables manual refresh.
The button shows a spinner while its repository refreshes and reports refusals in the notice line.
The store swaps in the returned state, so no extra fetch follows.

src/components/RepoRefreshButton.vue

@@ -0,0 +1,24 @@
+<script setup lang="ts">
+import { faArrowsRotate } from '@fortawesome/free-solid-svg-icons'
+import { FontAwesomeIcon } from '@fortawesome/vue-fontawesome'
+import { Button } from '@/components/ui/button'
+
+defineProps<{ repo: string; busy: boolean; blocked: boolean }>()
+defineEmits<{ refresh: [] }>()
+</script>
+
+<template>
+  <Button
+    variant="ghost"
+    size="icon-xs"
+    class="text-muted-foreground hover:text-link shrink-0"
+    :disabled="busy || blocked"
+    :aria-label="`Refresh ${repo}`"
+    :aria-busy="busy"
+    :title="`Refresh ${repo}`"
+    data-test="repo-refresh"
+    @click="$emit('refresh')"
+  >
+    <FontAwesomeIcon :icon="faArrowsRotate" :spin="busy" aria-hidden="true" />
+  </Button>
+</template>