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-phone-parser.php

@@ -20,7 +20,12 @@ final class PhoneParser
         // Find a run of digits, spaces, dashes, parens, dots and a leading '+',
         // with at least 10 digits in total. Walk candidates left-to-right and
         // pick the first that yields 10 or 11 digits.
-        if (!preg_match_all('/\+?[\d][\d\s().\-]{8,}/u', $text, $m)) {
+        // NOTE: the space class is a literal ' ' — not '\s'. If '\s' is used
+        // a newline or tab between two adjacent form fields (phone value,
+        // then checkbox value) would bleed into the phone and append extra
+        // digits. MessageFormatter/Classifier flatten fields with "\n" before
+        // calling us, so this matters in practice.
+        if (!preg_match_all('/\+?[\d][\d ().\-]{8,}/u', $text, $m)) {
             return null;
         }