feat(feed): optional per-feed sender-in-title toggle

Add a per-feed senderInTitle flag (domain FeedState.senderInTitle ↔
FeedConfig.sender_in_title). When set, the feed generator prefixes each
entry title with [Sender] (display name, falling back to the address).
Exposed as an admin edit-form checkbox and across the REST API
create/update/response schemas.

Co-Authored-By: Claude Opus 4.7 <[email protected]>

src/infrastructure/feed-mapper.ts

@@ -18,6 +18,7 @@ export function fromConfigDTO(dto: FeedConfig): FeedState {
     language: dto.language,
     mailboxId: dto.mailbox_id,
     author: dto.author,
+    senderInTitle: dto.sender_in_title,
     allowedSenders: dto.allowed_senders ?? [],
     blockedSenders: dto.blocked_senders ?? [],
     createdAt: dto.created_at,
@@ -34,6 +35,7 @@ export function toConfigDTO(state: FeedState): FeedConfig {
     language: state.language,
     mailbox_id: state.mailboxId,
     author: state.author,
+    sender_in_title: state.senderInTitle,
     allowed_senders: state.allowedSenders,
     blocked_senders: state.blockedSenders,
     created_at: state.createdAt,