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>

app/(app)/sessions/[id]/replay/page.tsx

@@ -0,0 +1,19 @@
+import type { Metadata } from "next";
+import { ReplayPlayerLoader } from "@/components/sessions/ReplayPlayerLoader";
+import { getSessionName } from "@/lib/db/queries/sessions";
+
+export async function generateMetadata({ params }: { params: Promise<{ id: string }> }): Promise<Metadata> {
+  const { id } = await params;
+  const name = await getSessionName(Number(id));
+  return { title: name ? `Replay ${name}` : "Replay" };
+}
+
+export default async function ReplayPage({ params }: { params: Promise<{ id: string }> }) {
+  const { id } = await params;
+  return (
+    <div className="flex flex-col gap-6">
+      <h1 className="font-heading text-2xl font-semibold">Replay</h1>
+      <ReplayPlayerLoader sessionId={Number(id)} />
+    </div>
+  );
+}