Add first and last name fields for users

This commit introduces optional `first_name` and `last_name` fields to the user model, including database migrations, backend, and frontend support. It enhances user profiles, updates user creation and editing flows, and refines the UI to display full names where available.

backend/alembic/versions/0009_user_profile_fields.py

@@ -0,0 +1,26 @@
+"""add user first and last name fields
+
+Revision ID: 0009_user_profile_fields
+Revises: 0008_service_settings
+Create Date: 2026-02-13
+"""
+
+from alembic import op
+import sqlalchemy as sa
+
+
+revision = "0009_user_profile_fields"
+down_revision = "0008_service_settings"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    op.add_column("users", sa.Column("first_name", sa.String(length=120), nullable=True))
+    op.add_column("users", sa.Column("last_name", sa.String(length=120), nullable=True))
+
+
+def downgrade() -> None:
+    op.drop_column("users", "last_name")
+    op.drop_column("users", "first_name")
+