NexaNote v0.2.7

fix: create WebDAV parent directories during sync push (#53)

Push was failing on the new file-based backend with 409 Conflicts on note
metadata/page uploads and a 500 Internal Server Error on the welcome
note. Root causes:

  - The WebDAV provider had no MKCOL support on the root collection, so
    notebook directories never persisted server-side. Subsequent PUTs to
    nested paths returned 409 (parent missing).
  - NotebookCollection.create_collection minted a fresh note id, so the
    slug returned to the caller no longer matched the slug the client
    requested — every follow-up PUT 409'd against the lost slug.
  - NoteCollection had no create_empty_resource, so PUT to a not-yet-
    existing page_N.ink (e.g. a new page during sync) bubbled up as a
    permission error.
  - NoteMetaFile.get_etag emitted a quoted token, which WsgiDAV's
    checked_etag rejects — every PUT to an existing note (the welcome
    note in particular) crashed with 500.
  - Writer crashes (DB errors, malformed JSON) propagated as bare 500
    responses instead of typed DAVErrors.

Fix:

  - RootCollection.create_collection materialises a notebook with an id
    whose first 8 hex chars match the slug, so MKCOL → PUT round-trips
    cleanly. NotebookCollection does the same for notes.
  - NoteCollection.create_empty_resource provisions new pages on PUT.
  - _NoteMetaWriter migrates the placeholder id to the client's id when
    the PUT body declares a different one.
  - get_etag now returns a quote-free token; WsgiDAV adds the quotes.
  - Writers convert exceptions into DAVError with a useful context_info,
    so callers get 400/500 with reasons instead of opaque "500 internal".
  - The server bootstraps the "Uncategorized" fallback notebook so the
    very first push from a fresh client has a valid parent collection.
  - The sync client MKCOLs missing parents on a 409 and retries the PUT
    once. Failure messages now include 5xx body snippets.

Tests:

  - tests/test_webdav_sync_push.py covers slug parsing, MKCOL idempotency,
    PUT into missing parents (live WsgiDAV server), end-to-end sync push,
    server bootstrap, and writer error reporting.

https://claude.ai/code/session_011hfnfHGLVJR1aUerZ5sZD6

Co-authored-by: Claude <noreply@anthropic.com>