build(orchestration): add dagster optional-dependency extra

Pins adjusted from >=1.8,<1.9 to >=1.12,<1.13 (dagster-webserver matching)
and >=0.28,<0.29 (dagster-postgres) — the 1.8.x/1.9.x/1.10.x lines cap at
Python <3.13 and the 1.11.x line caps at <=3.13.3; 1.12.x is the nearest line
that supports Python 3.13.6 (the venv runtime).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pyproject.toml

@@ -21,6 +21,7 @@ data = ["databento>=0.50"]
 web = ["fastapi>=0.110", "uvicorn[standard]>=0.29", "jinja2>=3.1", "httpx>=0.27"]
 pg = ["psycopg[binary]>=3.1"]
 factory = ["scipy>=1.11"]
+orchestration = ["dagster>=1.12,<1.13", "dagster-webserver>=1.12,<1.13", "dagster-postgres>=0.28,<0.29"]
 
 [project.scripts]
 fxhnt = "fxhnt.cli:app"