feat: service scaffold, k8s test infra, health

FastAPI + SQLAlchemy async + Alembic scaffold, src-layout (mirrors the
sowai-fiscal lib's own convention), pyproject wired to sowai-fiscal@v0.1.0
via git+https (uv.lock pins the commit). Makefile mirrors auto/Makefile's
k8s-test workflow: syncs into /app/fiscal-svc in the SAME auto-tests pod,
against a dedicated fiscal_svc_test database on the shared Postgres
sidecar, serialized by the SAME lock file the auto uses on purpose so the
two repos' test runs never race in the pod. Dockerfile installs git (the
git+https dependency needs it at uv sync time) and splits the dependency
layer from the project's own editable install for build caching.

GET /v1/health -> {"status": "ok"}, verified green via `make k8s-test`.

alembic/README

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+Generic single-database configuration with an async dbapi.

alembic/env.py

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+import asyncio
+from logging.config import fileConfig
+
+from sqlalchemy import pool
+from sqlalchemy.engine import Connection
+from sqlalchemy.ext.asyncio import async_engine_from_config
+
+from alembic import context
+
+from fiscal_svc.core.config import settings
+from fiscal_svc.core.db import Base
+
+# Uncomment as modules gain SQLAlchemy models, so autogenerate can see them
+# (mirrors auto/backend/alembic/env.py's own convention):
+# from fiscal_svc.tenancy import models as tenancy_models  # noqa: F401
+# from fiscal_svc.documents import models as documents_models  # noqa: F401
+
+# this is the Alembic Config object, which provides
+# access to the values within the .ini file in use.
+config = context.config
+config.set_main_option("sqlalchemy.url", settings.database_url)
+
+# Interpret the config file for Python logging.
+# This line sets up loggers basically.
+if config.config_file_name is not None:
+    fileConfig(config.config_file_name)
+
+# add your model's MetaData object here
+# for 'autogenerate' support
+target_metadata = Base.metadata
+
+# other values from the config, defined by the needs of env.py,
+# can be acquired:
+# my_important_option = config.get_main_option("my_important_option")
+# ... etc.
+
+
+def run_migrations_offline() -> None:
+    """Run migrations in 'offline' mode.
+
+    This configures the context with just a URL
+    and not an Engine, though an Engine is acceptable
+    here as well.  By skipping the Engine creation
+    we don't even need a DBAPI to be available.
+
+    Calls to context.execute() here emit the given string to the
+    script output.
+
+    """
+    url = config.get_main_option("sqlalchemy.url")
+    context.configure(
+        url=url,
+        target_metadata=target_metadata,
+        literal_binds=True,
+        dialect_opts={"paramstyle": "named"},
+    )
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+def do_run_migrations(connection: Connection) -> None:
+    context.configure(connection=connection, target_metadata=target_metadata)
+
+    with context.begin_transaction():
+        context.run_migrations()
+
+
+async def run_async_migrations() -> None:
+    """In this scenario we need to create an Engine
+    and associate a connection with the context.
+
+    """
+
+    connectable = async_engine_from_config(
+        config.get_section(config.config_ini_section, {}),
+        prefix="sqlalchemy.",
+        poolclass=pool.NullPool,
+    )
+
+    async with connectable.connect() as connection:
+        await connection.run_sync(do_run_migrations)
+
+    await connectable.dispose()
+
+
+def run_migrations_online() -> None:
+    """Run migrations in 'online' mode."""
+
+    asyncio.run(run_async_migrations())
+
+
+if context.is_offline_mode():
+    run_migrations_offline()
+else:
+    run_migrations_online()

alembic/script.py.mako

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+"""${message}
+
+Revision ID: ${up_revision}
+Revises: ${down_revision | comma,n}
+Create Date: ${create_date}
+
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+${imports if imports else ""}
+
+# revision identifiers, used by Alembic.
+revision: str = ${repr(up_revision)}
+down_revision: Union[str, Sequence[str], None] = ${repr(down_revision)}
+branch_labels: Union[str, Sequence[str], None] = ${repr(branch_labels)}
+depends_on: Union[str, Sequence[str], None] = ${repr(depends_on)}
+
+
+def upgrade() -> None:
+    """Upgrade schema."""
+    ${upgrades if upgrades else "pass"}
+
+
+def downgrade() -> None:
+    """Downgrade schema."""
+    ${downgrades if downgrades else "pass"}