fix: remove script_categories from Phase 4 RLS — no account_id column

script_categories is a global lookup table (shared across all tenants).
The account_id column belongs to ScriptTemplate in the same model file,
not ScriptCategory. The Python scan matched the file, not the class.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/alembic/versions/b3c7e9f2a1d8_enable_rls_phase4.py

@@ -12,6 +12,9 @@ Policy variants used:
 Skipped intentionally:
   - accounts            — IS the root table; no account_id column
   - plan_feature_defaults — platform config; no account_id column
+  - script_categories   — global lookup table; no account_id column
+                          (ScriptTemplate in the same file has account_id,
+                          ScriptCategory does not)
 
 Revision ID: b3c7e9f2a1d8
 Revises: 172ad76d7d20
@@ -54,7 +57,6 @@ _STANDARD_TABLES = [
     "psa_activity_logs",
     "psa_member_mappings",
     "script_builder_sessions",
-    "script_categories",
     "session_ratings",
     "tree_embeddings",
     "user_folders",