feat: due_at parser and event upserter

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BCrwHHnGCB5XH968Nxokqw

core/app/Ingest/ParsedDue.php

@@ -0,0 +1,60 @@
+<?php
+
+namespace App\Ingest;
+
+use App\Enums\DueMode;
+use App\Models\Event;
+use Carbon\CarbonImmutable;
+
+/** Разобранный due_at: tagged union по mode. */
+final class ParsedDue
+{
+    private function __construct(
+        public readonly DueMode $mode,
+        public readonly ?string $date,
+        public readonly ?string $time,
+        public readonly ?CarbonImmutable $instant,
+    ) {}
+
+    public static function local(string $date, string $time): self
+    {
+        return new self(DueMode::Local, $date, $time, null);
+    }
+
+    public static function fixed(CarbonImmutable $instant): self
+    {
+        return new self(DueMode::Fixed, null, null, $instant->utc());
+    }
+
+    /** Календарный день срока в данном поясе, Y-m-d. */
+    public function dayFor(string $tz): string
+    {
+        return match ($this->mode) {
+            DueMode::Local => $this->date,
+            DueMode::Fixed => $this->instant->setTimezone($tz)->format('Y-m-d'),
+        };
+    }
+
+    public function equals(Event $event): bool
+    {
+        if ($event->due_mode !== $this->mode) {
+            return false;
+        }
+
+        return match ($this->mode) {
+            DueMode::Local => $event->due_date->format('Y-m-d') === $this->date && $event->due_time === $this->time,
+            DueMode::Fixed => $event->due_instant->eq($this->instant),
+        };
+    }
+
+    /** @return array<string, mixed> колонки events */
+    public function columns(): array
+    {
+        return [
+            'due_mode' => $this->mode,
+            'due_date' => $this->date,
+            'due_time' => $this->time,
+            'due_instant' => $this->instant,
+        ];
+    }
+}