refactor(14-01): extract DKV inbox providers into shared inbox/ module

- Move ImapProvider, ExchangeInboxProvider, InboxProvider into apps/api/src/inbox/
- Move InboxConfig/InboxAttachment/InboxEmail into new inbox.types.ts
- dkv.types.ts re-exports the moved types so existing DKV imports keep compiling
- DKV switches import paths to ../inbox/... and imports InboxModule
- Pure move + import-path swap: fetchPdfAttachments and all DKV logic unchanged (D-01/D-02)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/api/src/inbox/inbox.module.ts

@@ -0,0 +1,19 @@
+import { Module } from '@nestjs/common';
+import { ExchangeInboxProvider } from './exchange-inbox.provider';
+import { ImapProvider } from './imap.provider';
+
+/**
+ * Shared inbox-connection module (IMAP/Exchange).
+ *
+ * Extracted out of DKV (D-01, 14-CONTEXT.md) so any module that needs to
+ * poll a mailbox — e.g. the Phase-14 EmailAlertAdapter (Plan 14-03) — can
+ * import InboxModule and inject ImapProvider / ExchangeInboxProvider without
+ * depending on DKV. DKV imports this module unchanged in behavior; each
+ * module keeps its own, independent mailbox configuration (D-03) — only the
+ * connection code is shared.
+ */
+@Module({
+  providers: [ImapProvider, ExchangeInboxProvider],
+  exports: [ImapProvider, ExchangeInboxProvider],
+})
+export class InboxModule {}