feat: make bootstrapper initialiser timeouts configurable

DefaultFlowStart and WorkspaceInit hardcoded the request timeouts for
their flow-svc and IAM calls, leaving operators no way to tune them for
high-latency environments (#874).

Expose them as constructor parameters threaded through the existing
initialiser `params:` mechanism, defaulting to the current values so
behaviour is unchanged unless explicitly overridden:

- DefaultFlowStart: list_timeout=10 (list-flows), start_timeout=30 (start-flow)
- WorkspaceInit: iam_timeout=10 (create-workspace)

Add unit tests for the defaults, override storage, and that configured
values reach the underlying request calls.

tests/unit/test_bootstrap/test_default_flow_start.py

@@ -0,0 +1,51 @@
+"""
+Unit tests for trustgraph.bootstrap.initialisers.DefaultFlowStart
+
+Verifies the list/start timeouts are configurable and that the
+configured values actually reach the flow-client request calls.
+"""
+
+from unittest.mock import AsyncMock, MagicMock
+
+from trustgraph.bootstrap.initialisers.default_flow_start import (
+    DefaultFlowStart,
+)
+
+
+def test_default_timeouts():
+    init = DefaultFlowStart(blueprint="bp")
+    assert init.list_timeout == 10
+    assert init.start_timeout == 30
+
+
+def test_timeout_overrides_are_stored():
+    init = DefaultFlowStart(blueprint="bp", list_timeout=5, start_timeout=99)
+    assert init.list_timeout == 5
+    assert init.start_timeout == 99
+
+
+async def test_run_forwards_configured_timeouts():
+    init = DefaultFlowStart(blueprint="bp", list_timeout=5, start_timeout=99)
+
+    # Flow client: list-flows returns no error + empty flow list,
+    # start-flow returns no error.
+    flow = MagicMock()
+    flow.start = AsyncMock()
+    flow.stop = AsyncMock()
+    flow.request = AsyncMock(side_effect=[
+        MagicMock(error=None, flow_ids=[]),  # list-flows response
+        MagicMock(error=None),               # start-flow response
+    ])
+
+    # Context: workspace "default" exists, hands back our mock flow client.
+    ctx = MagicMock()
+    ctx.logger = MagicMock()
+    ctx.config.keys = AsyncMock(return_value=["default"])
+    ctx.make_flow_client = MagicMock(return_value=flow)
+
+    await init.run(ctx, None, "v1")
+
+    calls = flow.request.call_args_list
+    assert len(calls) == 2
+    assert calls[0].kwargs["timeout"] == 5
+    assert calls[1].kwargs["timeout"] == 99