[nathanpixodeo]

Summary

• restore the literal email_from column when loading a template sender
• restore the email_from event context key and object property after sending
• keep the intended local $email_from variable rename from Qual: Fix 'SqlInjection' notices #39213

Root cause

The variable rename in #39213 accidentally converted literal SQL/object field names into dynamic references. With an initially empty sender value, the template query became SELECT rowid, FROM ... and failed before fetch_object().

Verification

• php -l htdocs/core/actions_sendmails.inc.php
• git diff --check
• focused SQLite proof: the previous generated query fails; the corrected query returns the template email_from
• source scan confirms all four corrupted dynamic references are gone

Fixes #39938