feat(collab): team-based pipeline sharing — spouses, partners, agents

[paruff]

Problem

Top investors work with teams: spouses, partners, agents, property managers. Current pipeline ownership is per-user only. No sharing.

Acceptance Criteria

• Create `Team` model: name, owner (User), created_at
• Create `TeamMember` model: team, user, role (owner/admin/member/viewer)
• Modify `PipelineProperty` to support team visibility: `team = ForeignKey(Team, null=True, blank=True)`
• Update all pipeline views to filter by `Q(user=request.user) | Q(team__members=request.user)`
• Add team creation/management UI at `/teams/`
• Invite flow: owner sends invite email → recipient accepts → added to team
• Role-based permissions: owner (full), admin (manage members), member (CRUD properties), viewer (read-only)
• E2E test: create team, invite member, verify shared pipeline visible
• Unit tests for permission logic

Implementation Guide (for opencode/mimo v2.5)

1. Create `Team` and `TeamMember` models in `core/models/team.py`
2. Add `team` FK to `PipelineProperty` model (migration needed)
3. Create `TeamPermission` helper class for view decorators
4. Create team views: create, invite, manage members, leave
5. Create `templates/teams/*.html` templates
6. Update all pipeline views to use `TeamPermission` queryset filtering
7. Add `/teams/` URL patterns
8. Tests in `tests/test_team_sharing.py`

Dependencies

• Requires: Pipeline CRM fully implemented (Phase 2 complete)
• Related: Issue fix(ci): remove commit-msg hook, add live model resolver #375 (agent/lender sharing) — extend sharing to external users