add Nostr publishing and bidirectional sync

- nostr/ vendors NostrEvent + the nostrclient WebSocket bridge from
  the events extension, retagged [TASKS] / subscription-id "tasks-*".
- nostr_publisher builds kind 31922 with the `event-type: task` tag
  (per aiolabs/webapp#25 — disambiguates from kind-31922 activities on
  shared relays), kind 31925 with task-status / occurrence /
  completed_at, and kind 5 deletions for both.
- nostr_hooks bridges task/completion mutations to the publisher and
  persists the resulting nostr_event_id back onto the local row.
- nostr_sync subscribes to {31922, 31925, 5/#k} and filters 31922
  client-side on `event-type: task` because most relays don't index
  custom single-letter tags.

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

nostr_publisher.py

@@ -0,0 +1,210 @@
+"""
+NIP-52 calendar-event publishing for the tasks extension.
+
+Builds:
+- kind 31922 task events (with `event-type: task` so the activities
+  feed can filter us out — see aiolabs/webapp#25 for context),
+- kind 31925 RSVP-shaped completion events (carrying `task-status`,
+  optional `occurrence`, and `completed_at`),
+- kind 5 deletes referencing either an `a` (for tasks) or `e` tag
+  (for completions).
+
+Signs with the wallet owner's Account keypair and publishes via the
+NostrClient wrapping nostrclient's WebSocket.
+"""
+
+import time
+
+import coincurve
+from loguru import logger
+
+from .models import Task, TaskCompletion
+from .nostr.event import NostrEvent
+
+
+def build_task_event(task: Task, pubkey: str) -> NostrEvent:
+    """Convert a Task to a NIP-52 kind 31922 calendar event tagged
+    `event-type: task` so it is recognizable as a task on shared relays."""
+    tags: list[list[str]] = [
+        ["d", task.d_tag],
+        ["title", task.title],
+        ["start", task.start_date],
+        ["event-type", "task"],
+    ]
+
+    if task.end_date:
+        tags.append(["end", task.end_date])
+    if task.location:
+        tags.append(["location", task.location])
+    if task.status:
+        tags.append(["status", task.status])
+
+    for cat in task.categories or []:
+        tags.append(["t", cat])
+
+    for participant in task.participants or []:
+        p_tag = ["p", participant.pubkey]
+        if participant.type:
+            # NIP-52 'p' tag accepts a 'relay' slot before role; we leave
+            # it empty (just ["p", pk, "", role]) to keep parity with the
+            # webapp emitter.
+            p_tag.extend(["", participant.type])
+        tags.append(p_tag)
+
+    if task.recurrence:
+        tags.append(["recurrence", task.recurrence.frequency])
+        if task.recurrence.day_of_week:
+            tags.append(["recurrence-day", task.recurrence.day_of_week])
+        if task.recurrence.end_date:
+            tags.append(["recurrence-end", task.recurrence.end_date])
+
+    nostr_event = NostrEvent(
+        pubkey=pubkey,
+        created_at=int(time.time()),
+        kind=31922,
+        tags=tags,
+        content=task.description or "",
+    )
+    nostr_event.id = nostr_event.event_id
+    return nostr_event
+
+
+def build_completion_event(
+    task_address: str, completion: TaskCompletion, pubkey: str
+) -> NostrEvent:
+    """Build a kind 31925 RSVP carrying our extension's `task-status` tag."""
+    tags: list[list[str]] = [
+        ["a", task_address],
+        ["task-status", completion.task_status],
+    ]
+    if completion.occurrence:
+        tags.append(["occurrence", completion.occurrence])
+    if completion.completed_at:
+        tags.append(["completed_at", str(completion.completed_at)])
+
+    nostr_event = NostrEvent(
+        pubkey=pubkey,
+        created_at=int(time.time()),
+        kind=31925,
+        tags=tags,
+        content=completion.notes or "",
+    )
+    nostr_event.id = nostr_event.event_id
+    return nostr_event
+
+
+def build_delete_task_event(task: Task, pubkey: str) -> NostrEvent:
+    """Kind 5 deletion of a (replaceable) kind 31922 task via its `a` tag."""
+    nostr_event = NostrEvent(
+        pubkey=pubkey,
+        created_at=int(time.time()),
+        kind=5,
+        tags=[
+            ["a", f"31922:{pubkey}:{task.d_tag}"],
+            ["k", "31922"],
+        ],
+        content="Task deleted",
+    )
+    nostr_event.id = nostr_event.event_id
+    return nostr_event
+
+
+def build_delete_completion_event(
+    completion_id: str, pubkey: str
+) -> NostrEvent:
+    """Kind 5 deletion of a kind 31925 completion via its `e` tag (the
+    completion is non-replaceable so we reference by event id, not address)."""
+    nostr_event = NostrEvent(
+        pubkey=pubkey,
+        created_at=int(time.time()),
+        kind=5,
+        tags=[
+            ["e", completion_id],
+            ["k", "31925"],
+        ],
+        content="Task unclaimed",
+    )
+    nostr_event.id = nostr_event.event_id
+    return nostr_event
+
+
+def sign_nostr_event(nostr_event: NostrEvent, private_key_hex: str) -> None:
+    privkey = coincurve.PrivateKey(bytes.fromhex(private_key_hex))
+    sig = privkey.sign_schnorr(bytes.fromhex(nostr_event.id))
+    nostr_event.sig = sig.hex()
+
+
+async def publish_task_to_nostr(
+    nostr_client,
+    task: Task,
+    account_pubkey: str,
+    account_prvkey: str,
+    *,
+    delete: bool = False,
+) -> NostrEvent | None:
+    if not nostr_client:
+        logger.debug("[TASKS] No NostrClient available, skipping publish")
+        return None
+    try:
+        nostr_event = (
+            build_delete_task_event(task, account_pubkey)
+            if delete
+            else build_task_event(task, account_pubkey)
+        )
+        sign_nostr_event(nostr_event, account_prvkey)
+        await nostr_client.publish_nostr_event(nostr_event)
+        logger.info(
+            f"[TASKS] Published {'delete' if delete else '31922 task'} "
+            f"{nostr_event.id[:16]}... (kind {nostr_event.kind})"
+        )
+        return nostr_event
+    except Exception as e:
+        logger.warning(f"[TASKS] Failed to publish task: {e}")
+        return None
+
+
+async def publish_completion_to_nostr(
+    nostr_client,
+    task_address: str,
+    completion: TaskCompletion,
+    account_pubkey: str,
+    account_prvkey: str,
+) -> NostrEvent | None:
+    if not nostr_client:
+        logger.debug("[TASKS] No NostrClient available, skipping publish")
+        return None
+    try:
+        nostr_event = build_completion_event(
+            task_address, completion, account_pubkey
+        )
+        sign_nostr_event(nostr_event, account_prvkey)
+        await nostr_client.publish_nostr_event(nostr_event)
+        logger.info(
+            f"[TASKS] Published 31925 completion {nostr_event.id[:16]}... "
+            f"(status: {completion.task_status})"
+        )
+        return nostr_event
+    except Exception as e:
+        logger.warning(f"[TASKS] Failed to publish completion: {e}")
+        return None
+
+
+async def publish_completion_delete_to_nostr(
+    nostr_client,
+    completion_id: str,
+    account_pubkey: str,
+    account_prvkey: str,
+) -> NostrEvent | None:
+    if not nostr_client:
+        return None
+    try:
+        nostr_event = build_delete_completion_event(completion_id, account_pubkey)
+        sign_nostr_event(nostr_event, account_prvkey)
+        await nostr_client.publish_nostr_event(nostr_event)
+        logger.info(
+            f"[TASKS] Published completion delete {nostr_event.id[:16]}..."
+        )
+        return nostr_event
+    except Exception as e:
+        logger.warning(f"[TASKS] Failed to publish completion delete: {e}")
+        return None