feat(messaging): sync draft emails and edit them in the thread composer (#22178)

Stop excluding drafts from sync across all three providers (Gmail DRAFT
label, Microsoft/IMAP Drafts folder) and add an isDraft boolean field on
Message so drafts are queryable by the API and AI agents.

Drafts render in the thread with a Draft tag; clicking one opens the
existing reply composer pre-filled with the draft's recipients, subject
and body, and Send reuses the existing send-email flow.

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Co-authored-by: Félix Malfait <felix.malfait@gmail.com>

packages/twenty-shared/src/metadata/constants/standard-object.constant.ts

@@ -1480,6 +1480,9 @@ export const STANDARD_OBJECTS = {
       deliveryStatus: {
         universalIdentifier: '209254fa-2b89-429d-a72a-c401c4bd5a78',
       },
+      isDraft: {
+        universalIdentifier: '20202020-4d3a-4b6e-9c1f-2a5e7b9d0c34',
+      },
       createdBy: {
         universalIdentifier: '6e52bde4-ed41-4462-aa70-121e496270b4',
       },