feat: Mini-Apps registry, Stammdaten backend persistence, bank accounts

- Register 6 mini-apps in kommunikation plugin (contact_picker, file_share,
  calendar_invite, mail_forward, ai_search, task_create)
- Connect AdressenTab to backend API (GET/POST/PATCH/DELETE /addresses)
- Create BankAccount model, schema, service, routes + migration 0033
- Connect KontenTab to backend API (GET/POST/PATCH/DELETE /bank-accounts)
- AI tools already working: 7 tools registered (hybrid_search, get_contact_mails, etc.)

alembic/versions/0033_bank_accounts.py

@@ -0,0 +1,45 @@
+"""Add bank_accounts table.
+
+Revision ID: 0033
+Revises: 0032_user_profile_fields
+Create Date: 2026-07-25
+"""
+
+from __future__ import annotations
+
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+from sqlalchemy.dialects.postgresql import UUID as PGUUID
+
+revision: str = "0033_bank_accounts"
+down_revision: Union[str, None] = "0032_user_profile_fields"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.create_table(
+        "bank_accounts",
+        sa.Column("id", PGUUID(as_uuid=True), primary_key=True, server_default=sa.text("gen_random_uuid()")),
+        sa.Column("tenant_id", PGUUID(as_uuid=True), nullable=False, index=True),
+        sa.Column("bank_name", sa.String(100), nullable=False),
+        sa.Column("iban", sa.String(34), nullable=False),
+        sa.Column("bic", sa.String(11), nullable=True),
+        sa.Column("account_holder", sa.String(200), nullable=True),
+        sa.Column("default_tax", sa.String(50), nullable=True),
+        sa.Column("is_default", sa.Boolean, nullable=False, server_default=sa.text("false")),
+        sa.Column("created_at", sa.DateTime(timezone=True), nullable=False, server_default=sa.func.now()),
+        sa.Column("updated_at", sa.DateTime(timezone=True), nullable=False, server_default=sa.func.now()),
+        sa.Column("deleted_at", sa.DateTime(timezone=True), nullable=True),
+    )
+
+    op.create_index("ix_bank_accounts_tenant", "bank_accounts", ["tenant_id"])
+    op.create_index("ix_bank_accounts_tenant_default", "bank_accounts", ["tenant_id", "is_default"])
+
+
+def downgrade() -> None:
+    op.drop_index("ix_bank_accounts_tenant_default", table_name="bank_accounts")
+    op.drop_index("ix_bank_accounts_tenant", table_name="bank_accounts")
+    op.drop_table("bank_accounts")