Add member-node association support

Members can now have multiple associated nodes, each with a public_key
and node_role (e.g., 'chat', 'repeater'). This replaces the single
public_key field on members with a one-to-many relationship.

Changes:
- Add MemberNode model for member-node associations
- Update Member model to remove public_key, add nodes relationship
- Update Pydantic schemas with MemberNodeCreate/MemberNodeRead
- Update member_import.py to handle nodes list in seed files
- Update API routes to handle nodes in create/update/read operations
- Add Alembic migration to create member_nodes table and migrate data
- Update example seed file with new format

alembic/versions/20241205_0001_002_member_nodes.py

@@ -0,0 +1,116 @@
+"""Add member_nodes association table
+
+Revision ID: 002
+Revises: 001
+Create Date: 2024-12-05
+
+"""
+
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+
+# revision identifiers, used by Alembic.
+revision: str = "002"
+down_revision: Union[str, None] = "001"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # Create member_nodes table
+    op.create_table(
+        "member_nodes",
+        sa.Column("id", sa.String(), nullable=False),
+        sa.Column("member_id", sa.String(36), nullable=False),
+        sa.Column("public_key", sa.String(64), nullable=False),
+        sa.Column("node_role", sa.String(50), nullable=True),
+        sa.Column(
+            "created_at",
+            sa.DateTime(timezone=True),
+            server_default=sa.func.now(),
+            nullable=False,
+        ),
+        sa.Column(
+            "updated_at",
+            sa.DateTime(timezone=True),
+            server_default=sa.func.now(),
+            nullable=False,
+        ),
+        sa.ForeignKeyConstraint(["member_id"], ["members.id"], ondelete="CASCADE"),
+        sa.PrimaryKeyConstraint("id"),
+    )
+    op.create_index("ix_member_nodes_member_id", "member_nodes", ["member_id"])
+    op.create_index("ix_member_nodes_public_key", "member_nodes", ["public_key"])
+    op.create_index(
+        "ix_member_nodes_member_public_key",
+        "member_nodes",
+        ["member_id", "public_key"],
+    )
+
+    # Migrate existing public_key data from members to member_nodes
+    # Get all members with a public_key
+    connection = op.get_bind()
+    members_with_keys = connection.execute(
+        sa.text(
+            "SELECT id, public_key FROM members WHERE public_key IS NOT NULL"
+        )
+    ).fetchall()
+
+    # Insert into member_nodes
+    for member_id, public_key in members_with_keys:
+        # Generate a UUID for the new row
+        import uuid
+
+        node_id = str(uuid.uuid4())
+        connection.execute(
+            sa.text(
+                """
+                INSERT INTO member_nodes (id, member_id, public_key, created_at, updated_at)
+                VALUES (:id, :member_id, :public_key, CURRENT_TIMESTAMP, CURRENT_TIMESTAMP)
+                """
+            ),
+            {"id": node_id, "member_id": member_id, "public_key": public_key},
+        )
+
+    # Drop the public_key column from members
+    op.drop_index("ix_members_public_key", table_name="members")
+    op.drop_column("members", "public_key")
+
+
+def downgrade() -> None:
+    # Add public_key column back to members
+    op.add_column(
+        "members",
+        sa.Column("public_key", sa.String(64), nullable=True),
+    )
+    op.create_index("ix_members_public_key", "members", ["public_key"])
+
+    # Migrate data back - take the first node for each member
+    connection = op.get_bind()
+    member_nodes = connection.execute(
+        sa.text(
+            """
+            SELECT DISTINCT member_id, public_key
+            FROM member_nodes
+            WHERE (member_id, created_at) IN (
+                SELECT member_id, MIN(created_at)
+                FROM member_nodes
+                GROUP BY member_id
+            )
+            """
+        )
+    ).fetchall()
+
+    for member_id, public_key in member_nodes:
+        connection.execute(
+            sa.text(
+                "UPDATE members SET public_key = :public_key WHERE id = :member_id"
+            ),
+            {"public_key": public_key, "member_id": member_id},
+        )
+
+    # Drop member_nodes table
+    op.drop_table("member_nodes")