[the-medo]

Quests can now manage recruitment and character participation end to end. GMs set quest status and open or close applications; players discover compatible quests, apply with a message, and withdraw or leave; GMs approve, decline, or remove participants.

Changes

• Add quest status/recruitment controls, character quest history, participant rosters, and persistent grid/list views.
• Enforce character ownership, quest-management permissions, world/system compatibility, and private application/message visibility. Finishing or abandoning a quest closes recruitment.
• Add migration 31 and participation/filter APIs; regenerate SQL queries, protobuf bindings, Swagger, and the frontend client while preserving existing protobuf field numbers and upgraded dependencies.

Validation

• Backend test suite and focused participation, permission, privacy, and protobuf compatibility tests passed.
• Frontend lint, formatting, TypeScript checks, Next.js production build, and Storybook build passed.
• Local HTTP and browser workflows passed for signup/login, recruitment, discovery, application editing/withdrawal, GM approval/decline, and quest status changes.
• Migration 30 → 31 → 30 → 31 and repeated migrations passed; API client regeneration is reproducible.
• Branch merges cleanly with the latest fetched main.

Deployment

Apply database migration 31 with the backend update before serving the updated frontend. Validation used isolated local development services; this PR does not deploy the app.