scaffold tasks extension

Empty skeleton mirroring the events extension layout: config/manifest,
pyproject + Makefile + ruff/mypy config, FastAPI routers wired into
tasks_ext, NostrClient bootstrap stubs, and an empty static/routes.json.

Models, migrations, CRUD, Nostr publisher/sync, and the API/template
layers land in follow-up commits.

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

README.md

@@ -0,0 +1,32 @@
+# Tasks — LNbits extension
+
+LNbits-side counterpart to the webapp `tasks` module. Stores and syncs
+recurring tasks / chores as Nostr NIP-52 calendar events.
+
+## Data model
+
+- **Kind 31922** — task (parameterized replaceable). Tagged with
+  `event-type: task` so activities consumers can filter it out
+  (see aiolabs/webapp#25 for context).
+- **Kind 31925** — task completion / RSVP-ish status update. Carries
+  `task-status` (`claimed`, `in-progress`, `completed`, `blocked`,
+  `cancelled`), an optional `occurrence` date for recurring tasks, and
+  `completed_at` when finalized.
+- **Kind 5** — NIP-09 deletions for the above.
+
+Recurrence is encoded as task-only tags: `recurrence` (`daily` |
+`weekly`), `recurrence-day` (weekday name for weekly), `recurrence-end`
+(YYYY-MM-DD).
+
+## What this extension does
+
+- Caches tasks and completions in a local sqlite/postgres schema.
+- Publishes mutations to Nostr via the `nostrclient` extension's
+  internal WebSocket bridge.
+- Subscribes to inbound 31922/31925 events filtered to `event-type=task`
+  so the local DB stays in sync with the relay set.
+
+## Status
+
+Early scaffold. Mirrors `events`' extension layout. See
+`~/dev/webapp/src/modules/tasks/` for the canonical client-side model.