Remove recordings feature, replay sessions directly, bump to 0.6.0

Recordings were just a thin named pointer over an already-captured
session's events, so the whole separate feature (recordings table, API
routes, pages, UI) is gone: any completed session can now be named and
replayed directly. Replaying no longer creates a session or duplicates
events of its own - it just bumps the source session's playCount/lastPlayedAt.

Also renames play_sessions/playSession(s) to sessions/session(s) throughout
the schema, queries, API routes, and UI for consistency, and updates the
README to match the new flow.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

components/sessions/ReplayPlayerLoader.tsx

@@ -0,0 +1,13 @@
+"use client";
+
+import dynamic from "next/dynamic";
+import { Skeleton } from "@/components/ui/skeleton";
+
+const ReplayPlayer = dynamic(() => import("./ReplayPlayer").then((m) => m.ReplayPlayer), {
+  ssr: false,
+  loading: () => <Skeleton className="h-64 w-full" />,
+});
+
+export function ReplayPlayerLoader({ sessionId }: { sessionId: number }) {
+  return <ReplayPlayer sessionId={sessionId} />;
+}