Add test client and automated integration test suite

- 'test' OAuth client maps to stefan's data via USER_ALIASES
- 38 tests covering OAuth (metadata, client_credentials, PKCE, invalid
  secret, no auth), Mail (accounts, folders, search), Calendar
  (calendars, tasks, events, search), Contacts (search, empty),
  Files (list, info), Notes (notebooks)
- Daily systemd timer (05:00) with NTFY notification on failure
- Shared token store (.active_tokens.json) for cross-process auth

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tests/run_tests.sh

@@ -0,0 +1,26 @@
+#!/bin/bash
+# MCP Server Integration Tests — laeuft taeglich via systemd timer
+set -uo pipefail
+
+LOG="/var/log/mcp-tests.log"
+NTFY_TOPIC="admin"
+VENV="/opt/mcp-servers/venv/bin"
+
+echo "[$(date)] MCP Tests gestartet" | tee -a "$LOG"
+
+OUTPUT=$($VENV/python -m pytest /opt/mcp-servers/tests/test_all.py -v --tb=short 2>&1)
+EXIT=$?
+
+echo "$OUTPUT" | tee -a "$LOG"
+
+if [ $EXIT -eq 0 ]; then
+    PASSED=$(echo "$OUTPUT" | grep -oP '\d+ passed' | head -1)
+    echo "[$(date)] MCP Tests OK: $PASSED" | tee -a "$LOG"
+else
+    FAILED=$(echo "$OUTPUT" | grep "FAILED" | head -5)
+    echo "[$(date)] MCP Tests FEHLGESCHLAGEN" | tee -a "$LOG"
+    /usr/local/bin/notify-ntfy "$NTFY_TOPIC" "MCP Tests fehlgeschlagen" \
+        "$(echo "$FAILED" | head -3)\n\nLog: tail -50 $LOG" "urgent" "x,test_tube"
+fi
+
+exit $EXIT