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>

app/worker.py

@@ -21,6 +21,7 @@ if os.environ.get('TINY_ADAPTER') == 'tiny':
     adapters['tiny'] = TinyOrders()
 last_tick = 0.0
 last_cleanup = 0.0
+last_tiny_keepalive = 0.0
 storage = LocalS3Storage()
 scan_thread = None
 render_thread = None
@@ -52,6 +53,27 @@ def tick():
                 c.execute("UPDATE dtf_local.outbox SET attempts=attempts+1, last_error=%s, available_at=now() + %s * interval '1 second' WHERE id=%s", (str(exc),delay,job['id']))
     last_tick = time.monotonic()
 
+def tiny_keepalive():
+    """Keep a connected Tiny authorised even while no orders are sent.
+
+    The refresh token expires unless it is used; access_token() refreshes (and
+    rotates) only when the access token is about to expire, so asking every few
+    minutes renews the connection roughly once per access-token lifetime.
+    """
+    global last_tiny_keepalive
+    if time.monotonic()-last_tiny_keepalive < 600:
+        return
+    last_tiny_keepalive = time.monotonic()
+    from . import tiny
+    if not tiny.configured():
+        return
+    try:
+        tiny.TinyAuth().access_token()
+    except tiny.TinyNotConnected:
+        pass
+    except Exception:
+        logging.exception('Tiny connection refresh failed')
+
 def loop():
     global last_cleanup
     while True:
@@ -60,6 +82,7 @@ def loop():
             if time.monotonic()-last_cleanup > 60:
                 cleanup()
                 last_cleanup = time.monotonic()
+            tiny_keepalive()
         except Exception:
             logging.exception('Local worker tick failed')
         time.sleep(1)