Add season field to episode scripts and improve global search; v2.0.50

Tag scripts with a season number (with an RSS-feed backfill for
existing uploads), surface it in search results, and fix word-boundary
matching plus a title/script-match dedup bug in the search merge logic.

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

server/state.js

@@ -54,7 +54,7 @@ export const state = {
   studyCertificates: [],
   studyCertificatesWritePromise: Promise.resolve(),
 
-  // episodeScripts: { [episodeNumber]: { text, title, filename, uploadedAt } }
+  // episodeScripts: { [episodeNumber]: { text, title, filename, season, uploadedAt } }
   episodeScripts: {},
   episodeScriptsWritePromise: Promise.resolve(),