refactor: rename lib/ to core/ for clearer core-module separation

Rename the top-level lib/ directory to core/ so the project root
immediately communicates which code is core platform and which lives
in modules/. PHP namespaces (MintyPHP\*) are unchanged — only the
Composer PSR-4 path mapping moves from lib/ to core/.

Module-internal lib/ directories (modules/*/lib/) are untouched.

Updated across the full stack:
- composer.json PSR-4 mapping
- bootstrap entry points (web/index.php, bin/*, tests/bootstrap.php)
- tooling configs (phpstan.neon, phpunit.xml, php-cs-fixer)
- 26 architecture contract tests
- enforcement-policy, guard-catalog, quality-gates
- all documentation (CLAUDE.md, README, 25 docs/, .agents/skills/)
- bin/qa-extended.sh search paths
- .claude/settings.local.json permission paths

Workflow: .agents/runs/CORE-LIB-RENAME-001/ (Analyst → Planner →
Executor → Code Review (4 findings fixed) → Security Review →
Acceptance Test → Finalizer)

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

core/Service/Scheduler/Handler/ScheduledJobHandlerInterface.php

@@ -0,0 +1,46 @@
+<?php
+
+namespace MintyPHP\Service\Scheduler\Handler;
+
+interface ScheduledJobHandlerInterface
+{
+    /**
+     * Returns the job definition (metadata + schedule defaults).
+     *
+     * The job_key is NOT included here – it is provided as the key in the
+     * registry handler map in ScheduledJobRegistry.
+     *
+     * Required keys:
+     *   label                        (string)       Human-readable name shown in admin UI.
+     *   description                  (string)       Short description of what the job does.
+     *   default_enabled              (int)          1 = enabled on first creation, 0 = disabled.
+     *   default_timezone             (string)       IANA timezone name (e.g. 'Europe/Berlin').
+     *   default_schedule_type        (string)       'hourly'|'daily'|'weekly'
+     *   default_schedule_interval    (int)          1..24 hourly / 1..365 daily / 1..52 weekly
+     *   default_schedule_time        (string|null)  'HH:MM', required for daily and weekly.
+     *   default_schedule_weekdays_csv(string|null)  CSV of ISO weekday numbers 1..7, weekly only.
+     *   default_catchup_once         (int)          1 = catch up once after downtime (default).
+     *   allowed_schedule_types       (array)        Subset of ['hourly','daily','weekly'].
+     */
+    public function definition(): array;
+
+    /**
+     * Executes the job and returns a normalized result envelope.
+     *
+     * Implementations are responsible for:
+     * - Calling the underlying service
+     * - Mapping service results to the envelope format below
+     * - Handling and wrapping service-level errors (e.g. lock_not_acquired → skipped)
+     *
+     * The result array content is job-specific and is JSON-encoded into the run log.
+     * Keep values JSON-serializable (no objects, no resources).
+     *
+     * @param int|null $actorUserId  Null for scheduler-triggered runs; user ID for manual runs.
+     * @return array{status:string, error_code:?string, error_message:?string, result:array}
+     *   status:        'success'|'failed'|'skipped'
+     *   error_code:    short machine-readable code, null on success
+     *   error_message: human-readable detail, null on success (max 255 chars)
+     *   result:        job-specific payload, empty array if nothing to report
+     */
+    public function execute(?int $actorUserId): array;
+}