Fix API mismatches, lint violations, and test failures

- enough_mail: use uidFetchMessage/uidMarkSeen/uidMarkFlagged/uidMove/
  uidMarkDeleted/uidExpunge, remove non-existent isUidSequence param,
  fix SmtpClient construction and use quit() not disconnect()
- Drift: add @DataClassName('MailboxRow') to avoid ugly 'Mailboxe',
  alias core model imports to resolve type name conflicts
- EmailsCompanion.insert: uid/receivedAt are required, not Value<T>
- Lint: remove unrecognised rules (prefer_const_collections,
  avoid_returning_null_for_future), add missing mounted guards after await
- Tests: fix html_utils expectations to match trim() behaviour,
  add explicit Map casts in email_model_test for avoid_dynamic_calls

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

analysis_options.yaml

@@ -10,6 +10,8 @@ analyzer:
     - lib/data/db/database.g.dart
     - "**/*.g.dart"
     - "**/*.freezed.dart"
+    # Vendored library — analyze only our own code
+    - "packages/**"
 
 linter:
   rules:
@@ -17,7 +19,6 @@ linter:
     - prefer_single_quotes
     - prefer_const_constructors
     - prefer_const_declarations
-    - prefer_const_collections
     - prefer_final_locals
     - prefer_final_in_for_each
     - unnecessary_const
@@ -30,7 +31,6 @@ linter:
     - avoid_dynamic_calls
     - avoid_empty_else
     - avoid_print
-    - avoid_returning_null_for_future
     - avoid_returning_null_for_void
     - avoid_type_to_string
     - cancel_subscriptions