feat(history): pin sessions to the top of the history tab (#886)

- Hold-menu Pin/Unpin action on session cards (PATCH /api/sessions/{id}
  with {pinned}, verified against the backend SessionRename model)
- Pinned sessions sort to the top on every load (client-side stable sort
  — the backend back-fills pins into page 1 but does not lift them)
- Pin indicator on pinned cards; search-result cards omit the pin action
- Tests: pin-first sort on load, toggle success (moves to top), failure
  (order kept + toast)

Co-authored-by: M57 <hy4ri@users.noreply.github.com>

app/src/main/java/com/m57/hermescontrol/data/remote/HermesApiService.kt

@@ -207,6 +207,14 @@ interface HermesApiService {
         @Body body: SessionRenameRequest,
     ): Response<Unit>
 
+    // Pin/unpin rides the same PATCH /api/sessions/{id} — body carries only
+    // {pinned} (backend SessionRename model, any subset accepted).
+    @PATCH("api/sessions/{id}")
+    suspend fun setSessionPinned(
+        @Path("id", encoded = true) sessionId: String,
+        @Body body: SessionRenameRequest,
+    ): Response<Unit>
+
     @POST("api/sessions/bulk-delete")
     suspend fun bulkDeleteSessions(
         @Body body: BulkDeleteRequest,