feat(backend): add new incentive task type for Reddit follow

Introduce a new incentive task type, REDDIT_FOLLOW, to encourage users to join the SurfSense community on Reddit. This includes a title, description, pages reward, and action URL for the task.

surfsense_backend/alembic/versions/83_add_reddit_follow_incentive_task.py

@@ -0,0 +1,35 @@
+"""Add REDDIT_FOLLOW to incentive task type enum
+
+Revision ID: 83
+Revises: 82
+
+Changes:
+1. Add REDDIT_FOLLOW value to incentivetasktype enum
+"""
+
+from collections.abc import Sequence
+
+import sqlalchemy as sa
+
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = "83"
+down_revision: str | None = "82"
+branch_labels: str | Sequence[str] | None = None
+depends_on: str | Sequence[str] | None = None
+
+
+def upgrade() -> None:
+    """Add REDDIT_FOLLOW to incentivetasktype enum."""
+    op.execute("ALTER TYPE incentivetasktype ADD VALUE IF NOT EXISTS 'REDDIT_FOLLOW'")
+
+
+def downgrade() -> None:
+    """Remove REDDIT_FOLLOW from incentivetasktype enum.
+    
+    Note: PostgreSQL doesn't support removing values from enums directly.
+    This would require recreating the enum type, which is complex and risky.
+    For safety, we leave the enum value in place during downgrade.
+    """
+    pass