fix(web): retire the stale homelab-era copy — neutral, accurate defaults on every page

Fixed: index.html meta description, empty-state sub and composer
placeholder (A1); app/config.py default suggestion chips → the four
neutral A2 defaults (BOR_SUGGESTIONS override unchanged); sources.html
KB page-sub → the current source model (git repos + local dirs +
uploaded archives, Sync pulls/imports); git-sources.html example URL
→ your-repo.git (A3); all 9 footers → neutral default in
span.footer-text (the phase-62 hook); E2E/unit conftests force the
code defaults so a local .env cannot leak corpus copy into tests;
new unit text pins + dedicated E2E suite.

Task 02 verification read-through — no change needed:
- sources.html sync result/error copy (matches the real sync behavior)
- tuning.html page-sub (accurate as written)
- history.html page-sub (accurate as written)
- doc-edit.html page-sub (accurate as written)
- git-sources.html page-sub (accurate as written)
- #sources-gate anonymous copy (accurate as written)

frontend/login.html

@@ -128,7 +128,7 @@
 
   <footer class="app-footer">
     <div class="container footer-inner">
-      <span>Powered by Reese's self-hosted models</span>
+      <span class="footer-text">Powered by self-hosted models</span>
     </div>
   </footer>