Implement core services for MVP-1 Personal Tracker CLI

Services implemented:
- session_service: Active session management (get/set/clear, validation)
- project_service: Project CRUD and directory structure
- note_service: Note handling and consolidation
- heuristics_service: Rule-based suggestions
- summary_service: Heuristic summary generation

tracker/cli/main.py

@@ -0,0 +1,7 @@
+"""Main CLI entry point."""
+import typer
+
+app = typer.Typer(
+    name="tracker",
+    help="Personal project tracker CLI",
+)