feat: add Convex project backend with generic storage and org-scoped authz
Schema:
- Cut projects table to {organizationId, name, description, createdAt, updatedAt}
- Add projectSources table with git source metadata and normalized URL index
- Add projectContextDocuments table with six canonical kinds, origin, revision
- Add by_organizationId index for project enumeration
- Remove all GitHub-specific fields (ownerId, provider, repoOwner, etc.)
Backend:
- Add requireCurrentOrganization and requireProjectMember authz helpers
- Migrate signals.ts authorizeProject to organizationId invariant check
- Update artifactModel: 8 operational artifacts (removed project/business/design.md)
- Add projectStore.ts with query/mutation/action store adapters
- Rewrite projects.ts to thin generic application calls
- Update projectIssues/projectArtifacts to use requireProjectMember
- Update projectEvents.test.ts and signals.test.ts for new project creation
All 33 backend tests pass.
224e98d0bc