security: enforce encrypted connections; pre-commit uses check-fast

IMAP/SMTP encryption:
- connectImap throws if account.imapSsl is false
- connectSmtp removes STARTTLS plaintext fallback; startTls failure is fatal
- Remove IMAP SSL/TLS toggle from add/edit account screens (always SSL)
- UI shows "IMAP (SSL/TLS)" section label to communicate the requirement

Pre-commit speed:
- Add check-fast task (analyze + unit + widget, no build-linux, no integration)
- pre-commit hook now runs task check-fast instead of task check
- task check remains the full suite for manual/CI use

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

.pre-commit-config.yaml

@@ -2,8 +2,8 @@ repos:
   - repo: local
     hooks:
       - id: task-check
-        name: task check (analyze + unit + widget + integration)
+        name: task check-fast (analyze + unit + widget)
         language: system
-        entry: task check
+        entry: task check-fast
         pass_filenames: false
         always_run: true