fix: phone leak, field-by-value detection, strict Flamingo email fallback

Three pilot-surfaced issues in one pass:

1. PhoneParser regex used '\s' in the candidate character class, so a
   digit on a following flattened line bled into the phone. '+7977
   6277470\n1' (phone + trailing checkbox value) parsed as 12 digits,
   producing '+797762774701'. Replaced '\s' with a literal space so
   newlines/tabs stop the candidate.

2. Custom-themed forms don't use 'your-name' / 'your-email' keys
   (washanyanya.ru has text-211 / text-212 / name_user). Added
   FieldDetector::find_name + find_email as fallbacks. Classifier
   and MessageFormatter now call them if no standard key matches,
   so 'Александр' in text-211 is recognised as a cyrillic name and
   scored / displayed accordingly.

3. FlamingoHelper copied '_from_email' into 'your-email' without
   validating it. Flamingo derives that meta from whatever field it
   considers "first"; on phone-first forms it ends up holding the
   phone number. Now we only copy _from_email if it contains '@',
   and dropped the _from_name shortcut entirely — FieldDetector
   handles the name via the actual field values.

Tests: +1 FieldDetectorTest (13 cases); +2 PhoneParserTest cases for
newline/tab bleeds; +1 ClassifierTest case; +1 MessageFormatterTest
case for custom field keys. Full suite 53/53 green.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

includes/class-message-formatter.php

@@ -35,7 +35,9 @@ final class MessageFormatter
 
         $phone = PhoneParser::parse(self::flatten_fields_for_phone($fields));
         $name = self::pick($fields, ['your-name', 'name', 'имя', 'fio']);
+        if ($name === '') $name = FieldDetector::find_name($fields);
         $email = self::pick($fields, ['your-email', 'email', 'e-mail', 'mail']);
+        if ($email === '') $email = FieldDetector::find_email($fields);
         $message = self::pick($fields, ['your-message', 'message', 'comment', 'сообщение', 'вопрос']);
 
         $lines = [];