chore(deps): bump opencite to >=0.5.3 (#315)

opencite 0.5.3 ships the search-task cancellation fix (neuromechanist/opencite#41):
search() now cancels and drains pending per-source tasks in a finally block, so a
wait_for timeout no longer orphans tasks that later touch closed HTTP clients.

Bump the floor to >=0.5.3 to require the fix and refresh uv.lock (0.5.2 -> 0.5.3).
No other packages change.

Author: neuromechanist

pyproject.toml

@@ -66,7 +66,7 @@ server = [
     "markdownify>=1.1.0",
     # Scheduling
     "apscheduler>=3.10.0,<4.0.0",
-    "opencite>=0.5.2",
+    "opencite>=0.5.3",
 ]
 
 observability = [