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/api/sessions/[id]/replay/route.ts

@@ -0,0 +1,31 @@
+import { NextResponse } from "next/server";
+import { getSessionForReplay, incrementSessionPlayCount } from "@/lib/db/queries/sessions";
+import { withRouteLogging } from "@/lib/api/with-route-logging";
+
+export const GET = withRouteLogging(
+  "sessions.replay-data",
+  async (_req: Request, { params }: { params: Promise<{ id: string }> }) => {
+    const { id } = await params;
+    const result = await getSessionForReplay(Number(id));
+    if (!result) return NextResponse.json({ error: "not found" }, { status: 404 });
+    if (result.session.durationMs === null) {
+      return NextResponse.json({ error: "session has no recorded duration yet" }, { status: 409 });
+    }
+    return NextResponse.json(result);
+  },
+);
+
+/**
+ * Marks the session as replayed (bumps playCount/lastPlayedAt). Replaying
+ * itself creates no session row or events of its own - the client just
+ * plays this session's already-recorded events back against newly-mapped
+ * devices, so this is the only DB write a replay run causes.
+ */
+export const POST = withRouteLogging(
+  "sessions.replay-start",
+  async (_req: Request, { params }: { params: Promise<{ id: string }> }) => {
+    const { id } = await params;
+    await incrementSessionPlayCount(Number(id), Date.now());
+    return NextResponse.json({ ok: true });
+  },
+);