feat(patient): soft-archive sessions with active/all/archived filter

Add archived + archived_at columns to PatientSession (setArchived stamps the
time). findByRecord/countByRecord accept an archived filter (default all to
keep existing callers, incl. the discount visit-count, unchanged); the
sessions GET reads ?filter=active|all|archived, defaulting to active so
archived visits are hidden. updateSession accepts { archived }. Records are
kept, only hidden. Verified end-to-end; docs updated.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

migrations/Version20260717111223.php

@@ -0,0 +1,29 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DoctrineMigrations;
+
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\Migrations\AbstractMigration;
+
+/**
+ * Auto-generated Migration: Please modify to your needs!
+ */
+final class Version20260717111223 extends AbstractMigration
+{
+    public function getDescription(): string
+    {
+        return 'Add archived + archived_at columns to patient_sessions (soft-archive)';
+    }
+
+    public function up(Schema $schema): void
+    {
+        $this->addSql('ALTER TABLE patient_sessions ADD archived TINYINT DEFAULT 0 NOT NULL, ADD archived_at INT DEFAULT NULL');
+    }
+
+    public function down(Schema $schema): void
+    {
+        $this->addSql('ALTER TABLE patient_sessions DROP archived, DROP archived_at');
+    }
+}