M6: browse notes by creation date (Timeline lens)

A temporal recall path — find a note by WHEN it was captured, not just what it contains (task 1903, first of the M6 recall items).

Backend: list_notes gains an optional created_at range (created_after / created_before, half-open interval) + sort=created; also lays groundwork for the richer-search facets (task 1902). New _parse_iso_dt helper with a DB-free unit test.

Frontend: a Timeline view (sidebar nav + 'g t' + command palette) grouping active notes newest-first into local-time buckets (Today / Yesterday / Earlier this week / this month / Month YYYY), plus an optional From/To date filter. Built as a lens on the same NoteCard masonry, consistent with the existing Reminders/Search views.

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

src/thoughtsync/notes.py

@@ -271,6 +271,12 @@ async def _rename_inbound_links(db, renamed: Note, old_title: str, new_title: st
         await _rewrite_links(db, source)
 
 
+def _parse_iso_dt(raw: str) -> datetime:
+    """Parse an ISO-8601 timestamp (accepting a trailing 'Z' for UTC), raising
+    ValueError on anything unparseable — used to validate date-range query params."""
+    return datetime.fromisoformat(raw.replace("Z", "+00:00"))
+
+
 @bp.get("")
 @login_required
 async def list_notes():
@@ -278,6 +284,14 @@ async def list_notes():
     if filter_name not in VALID_FILTERS:
         return jsonify({"error": "invalid filter"}), 400
     label_param = request.args.get("label")
+    # Optional creation-date range — the "browse by when" / Timeline lens. Both bounds
+    # are ISO-8601 instants forming a HALF-OPEN interval [created_after, created_before),
+    # so a client can pass local day-boundaries (start-of-day .. start-of-next-day)
+    # without off-by-one. `sort=created` orders newest-captured first for a chronological
+    # timeline; the default keeps the board's pinned/position/updated order.
+    after_param = request.args.get("created_after")
+    before_param = request.args.get("created_before")
+    sort = request.args.get("sort")
     async with session_scope() as db:
         stmt = select(Note).where(visible_to_user("note", Note.owner_id, Note.id, g.user_id))
         stmt = apply_filter(stmt, filter_name)
@@ -287,7 +301,20 @@ async def list_notes():
             except (ValueError, TypeError):
                 return jsonify({"error": "invalid label"}), 400
             stmt = stmt.where(Note.id.in_(select(NoteLabel.note_id).where(NoteLabel.label_id == lid)))
-        stmt = stmt.order_by(Note.pinned.desc(), Note.position.desc(), Note.updated_at.desc())
+        if after_param:
+            try:
+                stmt = stmt.where(Note.created_at >= _parse_iso_dt(after_param))
+            except ValueError:
+                return jsonify({"error": "invalid created_after"}), 400
+        if before_param:
+            try:
+                stmt = stmt.where(Note.created_at < _parse_iso_dt(before_param))
+            except ValueError:
+                return jsonify({"error": "invalid created_before"}), 400
+        if sort == "created":
+            stmt = stmt.order_by(Note.created_at.desc())
+        else:
+            stmt = stmt.order_by(Note.pinned.desc(), Note.position.desc(), Note.updated_at.desc())
         notes = (await db.scalars(stmt)).all()
         return jsonify({"notes": await _serialize_notes(db, notes)})