feat: inline entry title renaming (#14)

* feat: inline entry title renaming

- database.rs: add update_entry_title(conn, entry_uid, title) -> Result<bool>
  targets archived_entries table; returns false for unknown uid
- routes.rs: PATCH /api/archives/:archive_id/entries/:entry_uid (ROLE_USER)
  maps false -> 404; 3 tests (401 unauthed, 204+persists, 404 unknown uid)
- api.js: updateEntryTitle(archiveId, entryUid, title)
- ContextRail.jsx: click title h2 -> inline input; Enter/blur commits,
  Escape cancels (cancel ref prevents double-save on blur after Escape);
  pencil icon fades in on hover as edit affordance
- App.jsx: handleEntryTitleChange mutates entries + selectedEntry in-place
- styles.css: rail-title--editable cursor/hover, pencil icon show/hide,
  rail-title-input underline style
- rebuild frontend bundle

* chore: remove + prefix from Capture button label

frontend/src/api.js

@@ -25,6 +25,15 @@ export async function fetchEntryDetail(archiveId, entryUid) {
   return getJson(`/api/archives/${archiveId}/entries/${entryUid}`);
 }
 
+export async function updateEntryTitle(archiveId, entryUid, title) {
+  const res = await fetch(`/api/archives/${archiveId}/entries/${entryUid}`, {
+    method: 'PATCH',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify({ title: title ?? null }),
+  });
+  if (!res.ok) throw new Error(await res.text());
+}
+
 export async function fetchEntryTags(archiveId, entryUid) {
   return getJson(`/api/archives/${archiveId}/entries/${entryUid}/tags`);
 }