Initial commit: webmail client (M0/M1)

Three-pane webmail client.
- Backend: FastAPI + async SQLAlchemy + arq worker (Postgres/Redis), IMAP/SMTP
  sync, threading, search, drafts/outbox with undo, attachments, 2FA.
- Frontend: React 18 + Vite + TypeScript + TanStack Query + Tailwind; three-pane
  UI with rich-text composer, light/dark themes, resizable panels.

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

backend/app/outbox/schemas.py

@@ -0,0 +1,49 @@
+"""Compose/draft/send request & response models (SPEC §9.1)."""
+
+from __future__ import annotations
+
+import uuid
+
+from pydantic import BaseModel
+
+
+class DraftPayload(BaseModel):
+    to: list[str] = []
+    cc: list[str] = []
+    bcc: list[str] = []
+    subject: str = ""
+    html: str = ""
+    text: str = ""
+    attachment_ids: list[uuid.UUID] = []
+
+
+class DraftIn(BaseModel):
+    account_id: uuid.UUID
+    thread_id: uuid.UUID | None = None
+    reply_to_message_id: uuid.UUID | None = None
+    kind: str = "new"  # reply | reply_all | forward | new
+    payload: DraftPayload
+
+
+class DraftOut(BaseModel):
+    id: uuid.UUID
+    account_id: uuid.UUID
+    thread_id: uuid.UUID | None
+    reply_to_message_id: uuid.UUID | None
+    kind: str
+    payload: dict[str, object]
+    updated_at: str
+
+
+class SendRequest(BaseModel):
+    draft_id: uuid.UUID
+
+
+class SendResponse(BaseModel):
+    outbox_id: uuid.UUID
+    undo_until: str
+
+
+class OutboxStateOut(BaseModel):
+    outbox_id: uuid.UUID
+    state: str