Implement full Couch Potato movie & TV tracking app

Add all 10 milestones: Drizzle ORM + SQLite database with WAL mode,
Better Auth email/password authentication, TMDB API integration for
search and metadata import, TV season/episode caching, user tracking
(watchlist/status/watches/ratings with auto-transitions), discovery
feeds (continue watching, library, recommendations), US streaming
availability via TMDB providers, background job scheduler with
instrumentation hook, and dark cinema-themed frontend with DM Serif
Display + DM Sans typography and amber accent design system.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/api/episodes/[id]/watch/route.ts

@@ -0,0 +1,21 @@
+import type { NextRequest } from "next/server";
+import { NextResponse } from "next/server";
+import { AuthError, requireAuth } from "@/lib/api/auth-guard";
+import { unauthorized } from "@/lib/api/errors";
+import { logEpisodeWatch } from "@/lib/services/tracking";
+
+export async function POST(
+  _req: NextRequest,
+  { params }: { params: Promise<{ id: string }> },
+) {
+  let userId: string;
+  try {
+    userId = await requireAuth();
+  } catch (e) {
+    if (e instanceof AuthError) return unauthorized();
+    throw e;
+  }
+  const { id } = await params;
+  logEpisodeWatch(userId, id);
+  return NextResponse.json({ ok: true });
+}