Import: ThoughtSync-native round-trip + Google Keep Takeout

Complete the export/import pair (task 1907). POST /api/notes/import takes
an uploaded .zip and appends its notes — never overwriting existing ones.

Two formats, auto-detected:
- ThoughtSync export: recognized by its notes.json (app == thoughtsync);
  round-trips title/body/color/kind/pinned/archived/remind_at/timestamps/
  labels/items and re-attaches image media from the zip.
- Google Keep Takeout: each Keep <note>.json → a note. Maps title,
  textContent/listContent (+ checked), labels, Keep color enum (nearest
  palette match), isPinned/isArchived, isTrashed (→ trash), created/edited
  microsecond timestamps; folds annotation URLs into the body; resolves
  attachment filePaths relative to the note's folder.

Imported notes reuse create_note's derivation + reconciliation:
display-title derive, #tag reconcile, [[wiki-link]] rewrite. Explicit
labels attach as manual (via_tag=false); inline #tags reconcile as tags.
Image attachments copied into media storage; non-image types (e.g. Keep
audio) skipped until any-file attachments land.

Frontend: an Import control in the sidebar (next to Export) — hidden file
input + FormData POST + result toast ("Imported N notes (M skipped)"),
reloading the board + labels. New upload icon; notes-store importNotes().

Tests: import auth-guard + pure-helper coverage (_usec_to_dt, _keep_spec
list/text/color/annotation/attachment mapping, _native_spec round-trip).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FRgehjoz7Yv8LkUfADxACm

tests/test_notes.py

@@ -4,8 +4,11 @@ from thoughtsync.app import create_app
 from thoughtsync.models.note import NOTE_COLORS, Note
 from thoughtsync.notes import (
     _escape_like,
+    _keep_spec,
+    _native_spec,
     _parse_iso_dt,
     _slugify,
+    _usec_to_dt,
     derive_display_title,
     is_empty_note,
     normalize_color,
@@ -223,3 +226,80 @@ async def test_restore_revision_requires_auth(app):
         "/api/notes/00000000-0000-0000-0000-000000000000/revisions/00000000-0000-0000-0000-000000000001/restore"
     )
     assert resp.status_code == 401
+
+
+async def test_import_requires_auth(app):
+    client = app.test_client()
+    resp = await client.post("/api/notes/import")
+    assert resp.status_code == 401
+
+
+def test_usec_to_dt():
+    # Google Keep timestamps are microseconds since the epoch (UTC).
+    d = _usec_to_dt(1600000000000000)
+    assert d is not None and d.year == 2020 and d.tzinfo is not None
+    # garbage / missing → None (the note still imports, just without the timestamp)
+    assert _usec_to_dt("nope") is None
+    assert _usec_to_dt(None) is None
+
+
+def test_keep_spec_list_note():
+    kn = {
+        "title": "Groceries",
+        "listContent": [{"text": "Milk", "isChecked": False}, {"text": "Eggs", "isChecked": True}],
+        "labels": [{"name": "shopping"}],
+        "color": "TEAL",
+        "isPinned": True,
+        "isArchived": False,
+        "isTrashed": False,
+        "createdTimestampUsec": 1600000000000000,
+        "userEditedTimestampUsec": 1600000100000000,
+    }
+    spec = _keep_spec(kn, "Takeout/Keep")
+    assert spec["kind"] == "list"
+    assert spec["color"] == "teal"
+    assert spec["pinned"] is True
+    assert spec["archived"] is False
+    assert spec["trashed"] is False
+    assert spec["items"] == [{"text": "Milk", "checked": False}, {"text": "Eggs", "checked": True}]
+    assert spec["labels"] == ["shopping"]
+    assert spec["created_at"].year == 2020
+
+
+def test_keep_spec_text_note_folds_annotation_urls_and_maps_color():
+    kn = {
+        "textContent": "Read this later",
+        "annotations": [{"url": "https://example.com"}],
+        "color": "BROWN",  # no brown in our palette → nearest (orange)
+        "attachments": [{"filePath": "img.jpg", "mimetype": "image/jpeg"}],
+    }
+    spec = _keep_spec(kn, "Takeout/Keep")
+    assert spec["kind"] == "text"
+    assert "https://example.com" in spec["body"]
+    assert spec["color"] == "orange"
+    # attachment path is resolved relative to the note JSON's folder
+    assert spec["attachments"] == [{"file": "Takeout/Keep/img.jpg", "mime": "image/jpeg"}]
+
+
+def test_native_spec_roundtrip_fields():
+    n = {
+        "title": "T",
+        "body": "b",
+        "color": "blue",
+        "kind": "text",
+        "pinned": True,
+        "archived": False,
+        "created_at": "2026-07-19T00:00:00+00:00",
+        "labels": ["x"],
+        "items": [],
+        "attachments": [{"file": "attachments/ab/img.png", "mime": "image/png"}],
+    }
+    spec = _native_spec(n)
+    assert spec["title"] == "T"
+    assert spec["body"] == "b"
+    assert spec["color"] == "blue"
+    assert spec["pinned"] is True
+    assert spec["trashed"] is False  # exports only carry live notes
+    assert spec["created_at"].year == 2026
+    assert spec["labels"] == ["x"]
+    assert spec["attachments"] == [{"file": "attachments/ab/img.png", "mime": "image/png"}]