Add helper page around account linking and multiple emails

app/controllers/help_controller.rb

@@ -4,7 +4,8 @@ class HelpController < ApplicationController
   layout "help"
 
   PAGES = {
-    "hackorum-patch" => "Applying Patches with hackorum-patch"
+    "hackorum-patch" => "Applying Patches with hackorum-patch",
+    "account-linking" => "Account Linking & Multiple Emails"
   }.freeze
 
   def index

app/views/help/pages/account-linking.md

@@ -0,0 +1,29 @@
+# Account Linking & Multiple Emails
+
+If you use different email addresses on different devices (for example, a work address on your work laptop and a personal address on your phone), you can still use a single Hackorum account. Below are two supported ways to do that.
+
+## Option A: Connect one or more Google accounts
+
+Use this when you want to sign in with a different Google account on another device and keep using your existing Hackorum account.
+
+1. Go to **Settings → Account & Emails**.
+2. In **Connected accounts**, click **Connect Google account** and complete the Google OAuth flow.
+3. The Google identity will appear in the **Connected accounts** list.
+
+## Option B: Set a password and/or add emails
+
+Use this when you want to connect multiple addresses to the same account (for example, different mailing list identities). If you originally signed up with Google, you can still set a password later and use the standard email/password login.
+
+1. (Optional) Go to **Settings → Password** and set a password.
+2. Go to **Settings → Account & Emails**.
+3. Under **Email addresses**, add your second email and click **Send verification**.
+4. Verify the email via the link you receive.
+5. Repeat for any additional addresses you have used.
+
+These options keep everything in one account and ensure your mailing list activity is correctly attributed, regardless of which address you used.
+
+## Mailing list addresses
+
+If you have posted to the mailing list from multiple addresses over the years, add those addresses to your Hackorum account too. This ensures all of your past and future posts appear under one user account, no matter which email you used at the time.
+
+If you no longer have access to an old address (and cannot verify it), contact an administrator. They can add it to your account manually.