feat(v1.1.7-email-outbound): SMTP send/send_html

Outbound email reachable from scripts as email::send(#{...}) (plain
text) and email::send_html(#{...}) (multipart text + HTML). Backed by a
lettre SMTP relay configured from PICLOUD_SMTP_HOST/PORT/USER/PASSWORD/
TLS/TIMEOUT_SECS; if HOST/USER/PASSWORD aren't all set the service runs
in disabled mode (every send throws NotConfigured, warned at startup).

- EmailService trait + OutboundEmail DTO (picloud-shared);
  EmailServiceImpl + EmailTransport seam + lettre transport
  (manager-core), wired into the Services bundle and Rhai engine.
- Capability::AppEmailSend (→ script:write); seven-scope commitment held.
- Required-field + RFC5322-ish address validation; 25 MB per-message cap
  (PICLOUD_EMAIL_MAX_MESSAGE_BYTES). reply_to defaults to from.
- Per-call connection (pooling deferred to v1.2); no per-app from
  validation (operator's SMTP/SPF/DKIM concern).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/manager-core/src/lib.rs

@@ -31,6 +31,7 @@ pub mod dispatcher;
 pub mod docs_filter;
 pub mod docs_repo;
 pub mod docs_service;
+pub mod email_service;
 pub mod files_api;
 pub mod files_repo;
 pub mod files_service;
@@ -112,6 +113,10 @@ pub use dead_letters_api::{dead_letters_router, DeadLettersApiError, DeadLetters
 pub use dispatcher::{compute_backoff, Dispatcher, DispatcherError};
 pub use docs_repo::{DocsRepo, DocsRepoError, PostgresDocsRepo};
 pub use docs_service::DocsServiceImpl;
+pub use email_service::{
+    EmailConfig, EmailServiceImpl, EmailTransport, LettreEmailTransport, SmtpConfig, SmtpTls,
+    DEFAULT_EMAIL_MAX_MESSAGE_BYTES,
+};
 pub use files_api::{files_admin_router, FilesAdminState};
 pub use files_repo::{FilesConfig, FilesRepo, FilesRepoError, FsFilesRepo};
 pub use files_service::FilesServiceImpl;