feat(5.21): Tasks Plugin — activities with status, priority, due dates, ARQ reminders

- New builtin plugin app/plugins/builtins/tasks/ with full CRUD
- Task model with TenantMixin (title, description, status, priority, due_date, assigned_to, contact_id)
- Routes: GET/POST /tasks, GET/PATCH/DELETE /tasks/{id}, POST /tasks/{id}/assign, POST /tasks/{id}/status
- All routes RBAC-protected (tasks:read, tasks:write, tasks:delete)
- ARQ cron job tasks_due_reminder (daily 8:00) sends notifications for due tasks
- Migration 0001_initial.sql creates tasks table with indexes
- Frontend: Tasks.tsx page with list, filter, create/edit modal, detail modal
- Frontend: api/tasks.ts with React Query hooks
- Route /tasks in routes/index.tsx, sidebar entry via plugin manifest
- i18n keys for nav.tasks and tasks.* in de.json and en.json
- Tests: test_tasks.py (11 tests) + Tasks.test.tsx (3 tests)
- Registered TasksPlugin in conftest.py and worker.py

app/plugins/builtins/tasks/models.py

@@ -0,0 +1,49 @@
+"""Task model for the Tasks plugin."""
+
+from __future__ import annotations
+
+import uuid
+from datetime import datetime
+
+from sqlalchemy import DateTime, ForeignKey, Index, String, Text
+from sqlalchemy.dialects.postgresql import UUID as PGUUID
+from sqlalchemy.orm import Mapped, mapped_column
+
+from app.core.db import Base, TenantMixin
+
+
+class Task(Base, TenantMixin):
+    """Task entity — free activities (calls, notes, visits) linked to contacts."""
+
+    __tablename__ = "tasks"
+    __table_args__ = (
+        Index("ix_tasks_tenant_deleted", "tenant_id", "deleted_at"),
+        Index("ix_tasks_tenant_status", "tenant_id", "status"),
+        Index("ix_tasks_tenant_assigned", "tenant_id", "assigned_to"),
+        Index("ix_tasks_tenant_due", "tenant_id", "due_date"),
+        Index("ix_tasks_contact", "contact_id"),
+    )
+
+    id: Mapped[uuid.UUID] = mapped_column(
+        PGUUID(as_uuid=True), primary_key=True, default=uuid.uuid4
+    )
+    title: Mapped[str] = mapped_column(String(255), nullable=False)
+    description: Mapped[str | None] = mapped_column(Text, nullable=True)
+    status: Mapped[str] = mapped_column(
+        String(20), nullable=False, default="open"
+    )  # open, in_progress, done
+    priority: Mapped[str] = mapped_column(
+        String(10), nullable=False, default="medium"
+    )  # low, medium, high, urgent
+    due_date: Mapped[datetime | None] = mapped_column(
+        DateTime(timezone=True), nullable=True
+    )
+    assigned_to: Mapped[uuid.UUID | None] = mapped_column(
+        PGUUID(as_uuid=True), ForeignKey("users.id", ondelete="SET NULL"), nullable=True
+    )
+    contact_id: Mapped[uuid.UUID | None] = mapped_column(
+        PGUUID(as_uuid=True), ForeignKey("contacts.id", ondelete="SET NULL"), nullable=True
+    )
+    created_by: Mapped[uuid.UUID | None] = mapped_column(
+        PGUUID(as_uuid=True), ForeignKey("users.id", ondelete="SET NULL"), nullable=True
+    )