feat: homepage newsletter, Q&A callout, episodes page redesign, SEO/sitemap, asset tagging

- Fix "Invalid Date" on student account page (memberSince guard)
- Fix study community author showing full email instead of username
- Add newsletter sign-up section to homepage (between PRISM and Current Series)
- Add newsletter opt-in nudge to study enrollment flow
- Redesign episodes page: latest episode featured card + per-episode Spotify embed
- Add SEO description field to episodes page (visually hidden, admin-editable)
- Expand default sitemap paths to include /about, /contact, /episodes, /resources, /study, /study/titus, /study/colossians
- Add featured Q&A callout section to homepage
- Add Q&A callout to study hub footer
- Tag both untagged image assets in Asset Manager

data/admin-content-draft.json

@@ -1144,6 +1144,7 @@
         ]
       }
     ],
+    "episodesSeoIntro": "",
     "seo": {
       "title": "Verse by Verse with Nate",
       "description": "Verse by Verse with Nate explores Scripture one verse at a time with practical Bible teaching.",
@@ -1175,5 +1176,5 @@
       ]
     }
   },
-  "updatedAt": "2026-06-02T17:54:05.948Z"
+  "updatedAt": "2026-06-03T14:17:48.071Z"
 }