fix(alerts): broaden task detection to include Contact-linked tasks

Tasks with parentType='Contact' were invisible to AlertCalculator,
CaseContextBuilder, and OfficeContextBuilder — all queries only checked
parentType='Case'. This caused false "no preparation task" alerts in
the daily standup even when preparation tasks existed.

Broadens getSummary, findOverdueTasks, findUpcomingTasks, getWorkloadByUser
to query parentType=['Case','Contact']. Adds caseHasPreparation() helper
that checks Case tasks, Contact tasks, and NhActivity-linked tasks.
Adds getCaseContactIds() to CaseContextBuilder and OfficeContextBuilder.

Refs Task Master #1

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

manifest.json

@@ -3,11 +3,11 @@
     "module": "SmartAssistant",
     "description": "Unified AI Assistant for Legal CRM — floating chat with case memory, office alerts, and AI Gateway integration",
     "author": "klear",
-    "version": "2.7.2",
+    "version": "2.7.3",
     "acceptableVersions": [
         ">=8.0.0"
     ],
-    "releaseDate": "2026-04-09",
+    "releaseDate": "2026-04-14",
     "php": [
         ">=8.1"
     ]