feat(rules): project rule + topic suppressions

Lets a project mute individual rules or whole topics from rulebooks it
subscribes to, without unsubscribing the rulebook. Two new association
tables (migration 0060), 4 MCP tools (suppress/unsuppress × rule/topic),
4 REST endpoints, and an inline "× skip" affordance plus collapsed
"Suppressed (N)" section in the project's Rules tab.

get_applicable_rules now emits suppressed_rules and suppressed_topics
(detail objects with rulebook/topic context, not just IDs) so the UI
can render the suppressed list without a follow-up lookup. The main
rules projection grew topic_id and rulebook_id columns for the per-row
suppress affordance.

Project deletion cascades the suppression rows via hard DELETE — they
are pure associations with no soft-delete column, and restoring a
deleted project should start fresh, not inherit stale mutes.

Project-scoped rules (Rule.project_id) are deliberately not suppressible
— delete them with delete_rule instead.

Implements plan-task #187.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/fabledassistant/services/planning.py

@@ -59,6 +59,8 @@ async def start_planning(user_id: int, project_id: int, title: str) -> dict:
         "subscribed_rulebooks": applicable["subscribed_rulebooks"],
         "applicable_rules_truncated": applicable["truncated"],
         "project_rules": applicable.get("project_rules", []),
+        "suppressed_rules": applicable.get("suppressed_rules", []),
+        "suppressed_topics": applicable.get("suppressed_topics", []),
         "project_goal": getattr(project, "goal", "") or "",
         "open_task_count": open_count,
     }