feat(odoo-mail): sync partner upsert before firing async mails

Closes the register-then-immediately-forgot race for good. Two parallel
calls to /velxio/api/send-welcome and /velxio/api/send-password-reset
were hitting Odoo's REPEATABLE-READ snapshot timing: both workers took
their snapshot BEFORE either had committed the partner row, so each
ran its own INSERT and the second blew up on the velxio_user_id
unique constraint — costing one of the two emails.

Add a new sync_partner() helper that POSTs to a new Odoo route
/velxio/api/upsert-partner (lives in velxio_subscription) which only
upserts the partner — no mail, no subscription, fast. Register and
forgot-password await this BEFORE firing the async welcome / reset
tasks. Each user's flow is sequential at the Velxio HTTP layer, so
the snapshot race disappears.

sync_partner() reuses the existing _post() error-swallowing pattern.
If Odoo is down, sync_partner returns None and the await is a no-op
— the user still registers / gets the generic 200, the welcome /
reset endpoints retain their defensive upsert as a fallback path.

backend/app/api/routes/auth.py

@@ -91,9 +91,20 @@ async def register(
     token = create_access_token({"sub": user.id})
     _set_auth_cookie(response, token)
 
-    # Fire-and-forget welcome mail through Odoo. Registration MUST NOT
-    # block on this — if Odoo is down the user still gets in. We snapshot
-    # the fields we need so the task isn't tied to the SQLAlchemy session.
+    # Synchronously upsert the Odoo partner BEFORE firing the async
+    # welcome. This serializes partner creation at the Velxio HTTP
+    # layer so a subsequent forgot-password (or any other mail) lands
+    # on a partner whose existence is already committed — sidestepping
+    # the REPEATABLE-READ snapshot race two parallel mail workers
+    # would otherwise hit. `sync_partner` swallows its own errors and
+    # returns None if Odoo is down, so the user is never blocked.
+    await odoo_mail.sync_partner(
+        velxio_user_id=user.id,
+        email=user.email,
+        name=user.username,
+        country_code=user.signup_country or None,
+    )
+
     asyncio.create_task(
         odoo_mail.send_welcome(
             velxio_user_id=user.id,
@@ -210,6 +221,16 @@ async def forgot_password(
     reset_url = (
         f"{settings.FRONTEND_URL.rstrip('/')}/reset-password?token={plaintext}"
     )
+    # Same trick as register: ensure the Odoo partner exists synchronously
+    # before firing the async reset mail. Cheap (~50ms) and removes the
+    # REPEATABLE-READ snapshot race entirely.
+    await odoo_mail.sync_partner(
+        velxio_user_id=user.id,
+        email=user.email,
+        name=user.username,
+        country_code=user.signup_country or None,
+    )
+
     asyncio.create_task(
         odoo_mail.send_password_reset(
             email=user.email,

backend/app/services/odoo_mail.py

@@ -2,20 +2,33 @@
 
 Velxio leans on Odoo's outgoing-mail relay (SPF/DKIM already warmed up,
 templates editable from the admin UI) instead of running its own SMTP.
-The Odoo-side endpoints live in `velxio_transactional_mail` addon:
+The Odoo-side endpoints live in `velxio_transactional_mail` (mail) and
+`velxio_subscription` (partner upsert) addons:
 
-    POST <ODOO_URL>/velxio/api/send-welcome
-    POST <ODOO_URL>/velxio/api/send-password-reset
+    POST <ODOO_URL>/velxio/api/upsert-partner       (sync, fast)
+    POST <ODOO_URL>/velxio/api/send-welcome         (async, slow — SMTP)
+    POST <ODOO_URL>/velxio/api/send-password-reset  (async, slow — SMTP)
 
-Both expect a JSON-RPC payload (Odoo's `type='json'` controllers expect
+All expect a JSON-RPC payload (Odoo's `type='jsonrpc'` controllers expect
 `{"jsonrpc": "2.0", "params": {...}}`) and authenticate via the
 `X-Velxio-API-Key` header.
 
-These helpers are designed to be called from `asyncio.create_task(...)`
-so they NEVER raise into the request lifecycle. Any failure is logged at
-WARNING level and the function returns False. The result is otherwise
-ignored — registration / forgot-password succeed even when Odoo is down,
-the user just doesn't get the email until ops re-runs the cron.
+`sync_partner` is meant to be awaited synchronously. The mail helpers
+are designed to be called from `asyncio.create_task(...)` so they NEVER
+raise into the request lifecycle. Any failure is logged at WARNING level
+and the function returns False/None. Registration / forgot-password
+succeed even when Odoo is down — the user just doesn't get the email
+until ops re-runs the cron.
+
+Why the partner upsert is split out: Odoo's transaction isolation is
+REPEATABLE READ, so two parallel mail workers for the same brand-new
+user (register followed by an immediate forgot-password) would both
+take a snapshot before either committed the partner. Both would then
+INSERT, hitting the unique constraint on velxio_user_id and rolling
+back one of the two mails. Funnelling the partner upsert through a
+single synchronous call BEFORE the async mail tasks fire serializes
+the create at the Velxio HTTP layer and dodges the snapshot race
+entirely.
 """
 from __future__ import annotations
 
@@ -74,6 +87,35 @@ async def _post(endpoint: str, params: dict) -> Optional[dict]:
     return None
 
 
+async def sync_partner(
+    *,
+    velxio_user_id: str,
+    email: str,
+    name: Optional[str] = None,
+    country_code: Optional[str] = None,
+) -> Optional[int]:
+    """Synchronously ensure the Odoo partner for this user exists.
+
+    Caller awaits this BEFORE firing any async mail tasks so the
+    welcome / reset endpoints land on a partner the upsert already
+    committed. Returns the partner_id on success, None on any failure
+    (Odoo down, network error, etc.). The caller should ignore the
+    result and proceed — the user is registered/recovered regardless.
+    """
+    params: dict = {
+        "velxio_user_id": velxio_user_id,
+        "email": email,
+    }
+    if name:
+        params["name"] = name
+    if country_code:
+        params["country_code"] = country_code
+    result = await _post("/velxio/api/upsert-partner", params)
+    if result and "partner_id" in result:
+        return int(result["partner_id"])
+    return None
+
+
 async def send_welcome(
     *,
     velxio_user_id: str,