add models, migrations, and CRUD

Schema mirrors the webapp tasks module's ScheduledEvent + EventCompletion
shape:

- tasks.tasks (NIP-52 kind 31922 cache): (pubkey, d_tag) is the
  parameterized-replaceable key. JSON-encoded participants / categories
  / recurrence columns are decoded on read via _parse_task_row so each
  model can keep clean field validators.
- tasks.completions (kind 31925 cache): unique on
  (task_address, pubkey, occurrence). occurrence is NULL for one-shot
  tasks; create_completion deletes any prior claim for the same triple
  so the latest event wins.
- tasks.settings: singleton row with public_listing toggle.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

models.py

@@ -1 +1,156 @@
-# Pydantic models are filled in by the next commit.
+import json
+from datetime import datetime
+from typing import Literal
+
+from pydantic import BaseModel, Field, validator
+
+
+TaskStatus = Literal["claimed", "in-progress", "completed", "blocked", "cancelled"]
+
+
+class Participant(BaseModel):
+    pubkey: str
+    type: str | None = None  # "required" | "optional" | "organizer"
+
+
+class Recurrence(BaseModel):
+    frequency: Literal["daily", "weekly"]
+    day_of_week: str | None = None  # for weekly: monday..sunday
+    end_date: str | None = None  # YYYY-MM-DD, optional cutoff
+
+
+class CreateTask(BaseModel):
+    wallet: str | None = None  # filled from caller's wallet if absent
+    title: str
+    start_date: str  # YYYY-MM-DD or ISO datetime
+    end_date: str | None = None
+    description: str = ""
+    location: str | None = None
+    status: str = "pending"
+    event_type: str = "task"  # 'task' | 'announcement'
+    participants: list[Participant] = Field(default_factory=list)
+    categories: list[str] = Field(default_factory=list)
+    recurrence: Recurrence | None = None
+
+    @validator("participants", pre=True)
+    def parse_participants(cls, v):
+        if isinstance(v, str):
+            return json.loads(v) if v else []
+        return v or []
+
+    @validator("categories", pre=True)
+    def parse_categories(cls, v):
+        if isinstance(v, str):
+            return json.loads(v) if v else []
+        return v or []
+
+    @validator("recurrence", pre=True)
+    def parse_recurrence(cls, v):
+        if isinstance(v, str):
+            return json.loads(v) if v else None
+        return v
+
+
+class Task(BaseModel):
+    id: str
+    wallet: str
+    pubkey: str
+    d_tag: str
+    title: str
+    start_date: str
+    end_date: str | None = None
+    description: str = ""
+    location: str | None = None
+    status: str = "pending"
+    event_type: str = "task"
+    participants: list[Participant] = Field(default_factory=list)
+    categories: list[str] = Field(default_factory=list)
+    recurrence: Recurrence | None = None
+    nostr_event_id: str | None = None
+    nostr_event_created_at: int | None = None
+    time: datetime
+
+    @validator("participants", pre=True)
+    def parse_participants(cls, v):
+        if isinstance(v, str):
+            return json.loads(v) if v else []
+        return v or []
+
+    @validator("categories", pre=True)
+    def parse_categories(cls, v):
+        if isinstance(v, str):
+            return json.loads(v) if v else []
+        return v or []
+
+    @validator("recurrence", pre=True)
+    def parse_recurrence(cls, v):
+        if isinstance(v, str):
+            return json.loads(v) if v else None
+        return v
+
+    @property
+    def address(self) -> str:
+        """NIP-52 replaceable-event address (31922:pubkey:d-tag)."""
+        return f"31922:{self.pubkey}:{self.d_tag}"
+
+
+class PublicTask(BaseModel):
+    """Trimmed task payload for the public/anonymous endpoint."""
+
+    id: str
+    pubkey: str
+    d_tag: str
+    title: str
+    start_date: str
+    end_date: str | None = None
+    description: str = ""
+    location: str | None = None
+    status: str
+    event_type: str
+    participants: list[Participant] = Field(default_factory=list)
+    categories: list[str] = Field(default_factory=list)
+    recurrence: Recurrence | None = None
+
+    @validator("participants", pre=True)
+    def parse_participants(cls, v):
+        if isinstance(v, str):
+            return json.loads(v) if v else []
+        return v or []
+
+    @validator("categories", pre=True)
+    def parse_categories(cls, v):
+        if isinstance(v, str):
+            return json.loads(v) if v else []
+        return v or []
+
+    @validator("recurrence", pre=True)
+    def parse_recurrence(cls, v):
+        if isinstance(v, str):
+            return json.loads(v) if v else None
+        return v
+
+
+class CreateTaskCompletion(BaseModel):
+    task_address: str  # "31922:pubkey:d_tag"
+    task_status: TaskStatus = "claimed"
+    occurrence: str | None = None  # YYYY-MM-DD for recurring tasks
+    completed_at: int | None = None  # unix ts; set when task_status == 'completed'
+    notes: str = ""
+
+
+class TaskCompletion(BaseModel):
+    id: str  # Nostr event id (or local hash for not-yet-published)
+    task_address: str
+    pubkey: str  # claimer
+    occurrence: str | None = None
+    task_status: TaskStatus = "claimed"
+    completed_at: int | None = None
+    notes: str = ""
+    nostr_created_at: int
+    time: datetime
+
+
+class TasksSettings(BaseModel):
+    """Extension-level settings singleton."""
+
+    public_listing: bool = False  # expose /api/v1/tasks/public if enabled