refactor(semantics): migrate legacy @TIER to @COMPLEXITY annotations

- Replaced @TIER: TRIVIAL with @COMPLEXITY: 1
- Replaced @TIER: STANDARD with @COMPLEXITY: 3
- Replaced @TIER: CRITICAL with @COMPLEXITY: 5
- Manually elevated specific critical/complex components to levels 2 and 4
- Ignored legacy, specs, and node_modules directories
- Updated generated semantic map

backend/src/api/routes/health.py

@@ -1,5 +1,5 @@
 # [DEF:health_router:Module]
-# @TIER: STANDARD
+# @COMPLEXITY: 3
 # @SEMANTICS: health, monitoring, dashboards
 # @PURPOSE: API endpoints for dashboard health monitoring and status aggregation.
 # @LAYER: UI/API