feat(v1.1.8): email verification flow (migration 0028 + SDK)

migration 0028: app_user_email_verifications table — token_hash PK,
app_id + user_id FKs cascading, expires_at, consumed_at. Single-use
via atomic UPDATE WHERE consumed_at IS NULL.

UsersServiceImpl gains:
  * verifications: Arc<dyn AppUserVerificationRepo>
  * email: Arc<dyn EmailService>

users::send_verification_email(user_id, opts) mints a 32-byte token,
stores SHA-256(token), and calls EmailService::send with the body
template's {link} placeholder substituted by link_base + ?token=raw.
EmailError::NotConfigured propagates as UsersError::EmailNotConfigured
so scripts already handling email-disabled mode (v1.1.7 email::send)
don't need new branches.

users::verify_email(token) atomically consumes the one-shot token via
the verifications repo, marks the user's email_verified_at = NOW(),
and emits a "users::email_verified" event for future triggers.

Internal email send uses a synthesized SdkCallCx with principal=None
so the email-service AppEmailSend authz check is skipped (the
users::* surface has already gated on AppUsersWrite — the internal
hop isn't the script's direct call). Documented in HANDBACK §7.

EmailTemplateOpts now requires `from` (the v1.1.7 email service needs
an envelope sender). The brief example omitted it; deviation logged
in HANDBACK §7.

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

crates/executor-core/src/sdk/users.rs

@@ -530,6 +530,7 @@ fn parse_user_id(s: &str, ctx: &str) -> Result<AppUserId, Box<EvalAltResult>> {
 fn parse_email_template(opts: &Map, ctx: &str) -> Result<EmailTemplateOpts, Box<EvalAltResult>> {
     Ok(EmailTemplateOpts {
         link_base: required_string(opts, "link_base", ctx)?,
+        from: required_string(opts, "from", ctx)?,
         subject: required_string(opts, "subject", ctx)?,
         body_template: required_string(opts, "body_template", ctx)?,
     })