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>

tests/MessageFormatterTest.php

@@ -151,4 +151,31 @@ final class MessageFormatterTest extends TestCase
 
         self::assertStringContainsString('🟡 неясно', $r['text']);
     }
+
+    public function test_custom_form_field_keys_are_detected(): void
+    {
+        // washanyanya.ru-style form — fields are named text-NNN, name_user,
+        // etc. We must still pull out name + phone via value heuristics.
+        $fields = [
+            'text-211'     => 'Александр',
+            'text-212'     => '+79776277470',
+            'checkbox-382' => '1',
+        ];
+        $classification = Classifier::classify($fields, ['reason' => 'Akismet']);
+        $r = MessageFormatter::build([
+            'fields' => $fields, 'classification' => $classification,
+            'site_title' => 's.ru', 'form_title' => 'f',
+            'submitted_at' => '18.04.2026', 'reason' => 'Akismet',
+            'ip' => '', 'user_agent' => '', 'is_retro' => false,
+        ]);
+
+        // Name resolves to 'Александр' via FieldDetector
+        self::assertStringContainsString('Александр', $r['text']);
+        // Phone correctly parsed (11 digits, no trailing checkbox '1')
+        self::assertStringContainsString('+7 (977) 627-74-70', $r['text']);
+        // Email stays empty (no @-like value)
+        self::assertStringContainsString("📧 (не указан)", $r['text']);
+        // The checkbox value should still appear in 'Прочие поля'
+        self::assertStringContainsString('checkbox-382: 1', $r['text']);
+    }
 }