feat: connect Tiny through its v3 API with OAuth

Tiny v3 replaces the v2 token adapter. An operator connects Tiny once from
the Kanban; the callback is authorised by a single-use state, because Tiny's
cross-site redirect does not carry the SameSite=Strict operator cookie.
Tokens are kept in provider_tokens, the refresh token rotates under a row
lock, and the worker keeps the connection alive while order creation is off.

Orders find or create the customer's contact by CNPJ, then POST /pedidos
with product ids from TINY_PRODUCT_TEXTIL_FOLHA, _TEXTIL_AVULSA, _UV_FOLHA
and _UV_AVULSA and numeroOrdemCompra DTF-<number>; a retry searches the
customer's recent orders for that number first. The product settings avoid a
_FILE suffix, which the secrets loader reads as a secret file path.

Production passes the application credentials through but keeps
TINY_ADAPTER fake: Tiny has no sandbox, so creating real orders waits for a
supervised test. compose.providers.yaml gives the local API and worker an
internet route for provider testing; the default local stack still has none.

Verified with the full CI integration sequence locally, including the new
tiny_oauth_test against the real database.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/ROADMAP.md

@@ -237,13 +237,23 @@ From the report already sent. These are dated promises, not backlog.
   packaging weight/dimensions per length, subsidy policy.
 - `[~]` 1.3 — Idempotent Tiny/Olist order creation with order-number traceability.
   Confirm endpoints, tag behaviour and rate limits first.
-  **Groundwork (2026-09-24):** `app/tiny.py` (API 2.0) maps the approved
-  snapshot to `pedido.incluir` with `numero_pedido_ecommerce = DTF-<number>`,
-  searches for that number before creating, and treats Tiny's in-body errors
-  as failures so the outbox retries. Pickup keeps the existing `forma_envio X`
-  / DropStar convention. Selected with `TINY_ADAPTER=tiny`; tested against a
-  fake transport only. Product codes (`TINY_SKU_<MODE>`), the tag, API version
-  (2.0 vs 3.0) and rate limits must be confirmed on the client's account.
+  **Groundwork (2026-09-24), API v3 by decision:** OAuth2 against Tiny's
+  Keycloak. An operator starts the connection from the Kanban; the callback is
+  authorised by a single-use state (the operator cookie is SameSite=Strict and
+  does not survive Tiny's cross-site redirect). Tokens live in
+  `provider_tokens`; the refresh token rotates under a row lock and the worker
+  keeps the connection alive. Orders: contact found by CNPJ or created, then
+  `POST /pedidos` with product ids from `TINY_PRODUCT_TEXTIL_FOLHA` / `_TEXTIL_AVULSA` / `_UV_FOLHA`
+  / `_UV_AVULSA` (not `_<MODE>`: a name ending in `_FILE` is read as a secret
+  file path by `app/core/secrets.py`) and
+  `numeroOrdemCompra = DTF-<number>`; a retry searches the customer's last
+  seven days of orders for that number first. Production passes the app
+  credentials through but keeps `TINY_ADAPTER: fake`. Tested against fake
+  transports (`tests.test_tiny`) and, for OAuth, the real database
+  (`tests.tiny_oauth_test`). Tiny has no sandbox: the first real test creates
+  real orders. Still to confirm on the client's account: plan (Construa+),
+  product ids, token lifetimes, whether pickup needs a transportador, and
+  rate limits.
 - `[~]` 1.4 — Final print-file generation (see 3.2 and 3.6: production instructions
   must survive checkout before an output engine can reproduce the approved job).
   **Built (2026-09-24):** each paid item gets a PDF the width of the film and