feat: insurance section — overview, documents, analysis, KVG premium comparison

- Insurance overview page (/insurance): current policies table with type,
  provider, premium, franchise, coverage, and document links
- Documents page: upload and manage insurance documents
- Analysis page: coverage gap analysis per insurance type
- Priminfo integration (/insurance/priminfo): KVG premium comparison by
  insurer, model (TAR/HMO/etc.), franchise level, and accident coverage
  via embedded Priminfo iframe (no public API available)
- Backend: Insurance, PraemienEntry, PraemienPolice models with migrations
- Sidebar: insurance nav group with flyout and dropdown
- i18n: all keys in DE/EN/FR/IT

backend/finance/migrations/0022_add_praemien_entry.py

@@ -0,0 +1,34 @@
+# Generated by Django 6.0.4 on 2026-05-24 11:14
+
+from django.db import migrations, models
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('finance', '0021_add_insurance_model'),
+    ]
+
+    operations = [
+        migrations.CreateModel(
+            name='PraemienEntry',
+            fields=[
+                ('id', models.BigAutoField(auto_created=True, primary_key=True, serialize=False, verbose_name='ID')),
+                ('plz', models.CharField(db_index=True, max_length=10)),
+                ('ort', models.CharField(max_length=200)),
+                ('kanton', models.CharField(max_length=2)),
+                ('region', models.PositiveSmallIntegerField()),
+                ('bfs_nr', models.PositiveIntegerField(db_index=True)),
+                ('gemeinde', models.CharField(max_length=200)),
+                ('bezirk', models.CharField(blank=True, default='', max_length=200)),
+                ('avg_adult', models.DecimalField(decimal_places=2, max_digits=8)),
+                ('avg_young_adult', models.DecimalField(decimal_places=2, max_digits=8)),
+                ('avg_child', models.DecimalField(decimal_places=2, max_digits=8)),
+                ('data_year', models.PositiveSmallIntegerField(db_index=True)),
+            ],
+            options={
+                'ordering': ['kanton', 'ort'],
+                'unique_together': {('plz', 'ort', 'data_year')},
+            },
+        ),
+    ]