Fix mobile nav/TOC/overflow on article pages + harden membership form

Mobile fixes (article, guide, get-to-know, projects pages):
- Remove duplicate main.js include site-wide. footer.js emitted a
  <script src=main.js> inside the footer block while pages also load one
  before </body>, so DOMContentLoaded ran twice and every tap toggled the
  mobile menu / article TOC twice (net no-op). Menu and TOC only worked on
  the homepage. Now exactly one main.js per page, before </body>.
- Kill horizontal overflow: add overflow-x: clip to html/body (clips the
  off-canvas mobile nav panel without breaking position: sticky, unlike
  overflow-x: hidden).
- Reset align-items to stretch in the mobile .article-layout-container
  rule; the desktop flex-start made .article-container size to max-content
  width in a column flexbox and overflow the viewport.

Membership form hardening (Become a Member):
- Honeypot field + localStorage cooldown (30s gap, max 3/24h) + stronger
  email regex; trilingual cooldown alert message.
- Apps Script (setup doc): per-email auto-reply dedupe + daily send cap;
  applicant reply is a plain thank-you that never echoes submitted answers.
- Draft HTML welcome email (email-welcome-preview.html) for later use.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

css/base/_base.css

@@ -23,19 +23,21 @@
   
   html {
       /*
-       * POMEMBNO: Ta selektor naj ostane brez `overflow` pravil.
-       * `overflow-x: hidden` na `<html>` ali `<body>` elementu preprečuje
-       * pravilno delovanje `position: sticky`, ki ga uporablja stranska
-       * vrstica v člankih.
+       * `overflow-x: hidden` na `<html>`/`<body>` bi pokvaril `position: sticky`
+       * (stranska vrstica in mobilni TOC v člankih). Zato uporabljamo
+       * `overflow-x: clip`, ki obreže vodoravni preliv (npr. mobilni meni,
+       * ki je zunaj zaslona), NE da bi ustvaril drsni vsebnik, zato `sticky`
+       * še vedno deluje.
       */
+      overflow-x: clip;
   }
-  
+
   body {
       font-family: 'Inter', sans-serif;
       margin: 0;
       background-color: #FFFFFF;
       color: #101828;
-      /* `overflow-x: hidden;` je bil odstranjen, da omogoči pravilno delovanje `position: sticky`. */
+      overflow-x: clip;
   }
   
   /* Pravilo za preprečevanje drsenja, ko je mobilni meni odprt. To je pravilno in ostane. */