fix: update_page properties now update in-place via upsertBlockProperty

[nlsn]

Closes #48

Problem

update_page called with a properties dict and no content was routing
through _set_page_level_properties → logseq.Editor.setPageProperties.
In practice, setPageProperties appended a new block to the page body with
properties serialized as text, rather than updating the existing page-level
property lines in place. The appended block was invisible to Logseq's property
system and the success message was misleading.

Secondary bug: tag values were serialized as Python list repr (['mcp-test'])
instead of Logseq syntax ([[mcp-test]]).

Fix

In src/mcp_logseq/logseq.py, update_page_with_blocks: replaced the
_set_page_level_properties call (and the pre-fetch via
_get_page_level_properties) with a single call to _update_page_properties.

That method calls logseq.Editor.upsertBlockProperty once per key on the
first block (the page-properties pre-block), updating values in place and
implicitly preserving untouched keys.

The tags serialization bug is also resolved — upsertBlockProperty receives a
proper Python list and Logseq renders it correctly as [[tag]] references.

Tests Added

• test_update_page_properties_only_updates_in_place — regression test;
  asserts no setPageProperties/appendBlockInPage call, and exactly N
  upsertBlockProperty calls targeting the first block
• Updated test_update_page_append_mode_merges_properties and
  test_update_page_replace_mode_replaces_properties to match new API call
  sequence and result shape

[nlsn]

Hi @ergut - before merging, I want to flag a potential secondary issue I haven't had time to investigate yet.

The fix routes tag values through upsertBlockProperty with a Python list, which Logseq renders as [[wikilink]]-style page references. This may be the correct behavior, but I want to verify it's consistent with what create_page produces for tags, and that it matches user expectations — plain tags and page references behave differently in Logseq (backlinks, page creation, etc.).

Could you hold off on merging until I've had a chance to test this? Thanks for your patience.