fix: resolve IMMUTABLE function errors in database migrations

Fixed multiple PostgreSQL migration errors:

1. alembic/versions/a1b2c3d4e5f6_add_performance_indexes_v1_0_0.py:
   - idx_logs_recent: Removed NOW() - INTERVAL condition
     Now uses simple btree index with DESC ordering
   - idx_apikeys_valid: Removed NOW() condition
     Now uses simple partial index on is_active only

   PostgreSQL doesn't allow non-IMMUTABLE functions in index predicates.
   NOW() is STABLE, not IMMUTABLE, because it returns different values over time.

2. alembic/versions/b2c3d4e5f6a7_create_archive_tables_v1_0_0.py:
   - Removed partitioning from scenario_logs_archive
   - Removed partitioning from scenario_metrics_archive

   DATE_TRUNC() in partition key is not IMMUTABLE.
   Tables work without partitioning for now.

3. alembic.ini:
   - Changed localhost to postgres (already done in previous commit)

Migrations now run successfully without IMMUTABLE errors.

alembic/versions/a1b2c3d4e5f6_add_performance_indexes_v1_0_0.py

@@ -136,12 +136,13 @@ def upgrade() -> None:
         postgresql_using="btree",
     )
 
-    # Recent logs (last 30 days - for active monitoring)
-    op.execute("""
-        CREATE INDEX idx_logs_recent 
-        ON scenario_logs (scenario_id, received_at) 
-        WHERE received_at > NOW() - INTERVAL '30 days'
-    """)
+    # Recent logs index - ordered by received_at DESC for recent queries
+    op.create_index(
+        "idx_logs_recent",
+        "scenario_logs",
+        ["scenario_id", sa.text("received_at DESC")],
+        postgresql_using="btree",
+    )
 
     # Active API keys
     op.create_index(
@@ -152,13 +153,14 @@ def upgrade() -> None:
         postgresql_using="btree",
     )
 
-    # Non-expired API keys
-    op.execute("""
-        CREATE INDEX idx_apikeys_valid 
-        ON api_keys (user_id, created_at) 
-        WHERE is_active = true 
-        AND (expires_at IS NULL OR expires_at > NOW())
-    """)
+    # Active API keys (valid ones - is_active flag only, can't use NOW() in index predicate)
+    op.create_index(
+        "idx_apikeys_valid",
+        "api_keys",
+        ["user_id", "created_at"],
+        postgresql_where=sa.text("is_active = true"),
+        postgresql_using="btree",
+    )
 
     # =========================================================================
     # 3. INDEXES FOR N+1 QUERY OPTIMIZATION

alembic/versions/b2c3d4e5f6a7_create_archive_tables_v1_0_0.py

@@ -68,8 +68,8 @@ def upgrade() -> None:
             postgresql.UUID(as_uuid=True),
             nullable=True,
         ),
-        # Partition by month for efficient queries
-        postgresql_partition_by="RANGE (DATE_TRUNC('month', received_at))",
+        # Note: Partitioning removed - DATE_TRUNC is not IMMUTABLE
+        # For large datasets, consider adding a computed 'month' column
     )
 
     # Create indexes for archive table
@@ -143,7 +143,7 @@ def upgrade() -> None:
             sa.Integer(),
             nullable=True,
         ),
-        postgresql_partition_by="RANGE (DATE_TRUNC('month', timestamp))",
+        # Note: Partitioning removed - DATE_TRUNC is not IMMUTABLE
     )
 
     # Create indexes for metrics archive