Add VO management, tariff-option assignment, and 2-step schaltung wizard

VOs (Vertriebspartner-Nummern)
- New vos table (one row per VO, scoped to a provider). Migrations
  add tarife.vo_id and schaltungen.vo_id columns (nullable so legacy
  rows survive).
- New /api/vos CRUD (list, create, update, delete with use-checks).
- Admin: new "VOs (Vertriebspartner)" sub-tab. List/create with
  provider dropdown; edit via prompt; delete refuses while used.
- /api/tarife?vo_id=X filter for fetching tariffs of a specific VO.

Tariff editor
- Add-tariff form requires a VO; new dependent VO dropdown that
  populates after the provider is chosen.
- Edit-tariff modal now shows the VO dropdown and a checkbox grid of
  all anbieter-wide tarifoptionen. Saving the dialog applies the
  selection via the existing tarifoptionen_tarife table.
- New GET /api/tarife/:id/tarifoptionen-multi returns the option set
  scoped to the tariff's provider, each annotated with whether it is
  currently assigned to this tariff.
- POST/PUT /api/tarife accept vo_id (required for create, validated
  against the provider) and an optional tarifoption_ids array.

Schaltung wizard
- The Schaltung-erfassen tab is now a 2-step wizard:
  step 1 picks a provider from a button row (mirrors the screenshot
  the user shared); step 2 shows a 2-column form mirroring the
  Aktivierungs-/Vertragsdaten layout.
- Step 2 cascades: VO -> tariffs filtered by VO -> tarifoptionen
  filtered by tariff. Erfasser is autofilled from the logged-in user
  (read-only).
- Removed customer fields that the user does not need (Kundennummer,
  Kennwort/Service-PIN never existed; Rufnummer is now optional both
  in the form and in the API validation).
- After saving, the wizard resets to step 1 ready for the next entry.

Schema
- tarife: vo_id added.
- schaltungen: vo_id added; rufnummer is nullable in new DBs.
  Existing DBs may still have NOT NULL on rufnummer; the schaltungen
  route now sends an empty string instead of NULL to remain
  compatible.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

routes/vos.js

@@ -0,0 +1,92 @@
+const express = require('express');
+const db = require('../db');
+const asyncHandler = require('../middleware/asyncHandler');
+
+const router = express.Router();
+
+// List all VOs (optionally filtered by anbieter via ?anbieter_id=)
+router.get('/', asyncHandler(async (req, res) => {
+    const { anbieter_id } = req.query;
+    if (anbieter_id) {
+        const rows = await db.all(
+            `SELECT v.*, a.name AS anbieter_name
+             FROM vos v JOIN anbieter a ON v.anbieter_id = a.id
+             WHERE v.anbieter_id = ? AND v.aktiv = 1
+             ORDER BY v.nummer`,
+            [anbieter_id]
+        );
+        return res.json(rows);
+    }
+    const rows = await db.all(
+        `SELECT v.*, a.name AS anbieter_name
+         FROM vos v JOIN anbieter a ON v.anbieter_id = a.id
+         ORDER BY a.name, v.nummer`
+    );
+    res.json(rows);
+}));
+
+router.post('/', asyncHandler(async (req, res) => {
+    const { anbieter_id, nummer, bezeichnung } = req.body || {};
+    if (!anbieter_id) return res.status(400).json({ error: 'Anbieter ist erforderlich' });
+    if (!nummer || !String(nummer).trim()) return res.status(400).json({ error: 'VO-Nummer ist erforderlich' });
+    try {
+        const result = await db.run(
+            'INSERT INTO vos (anbieter_id, nummer, bezeichnung) VALUES (?, ?, ?)',
+            [anbieter_id, String(nummer).trim(), bezeichnung ? String(bezeichnung).trim() : null]
+        );
+        res.json({ id: result.lastID, anbieter_id, nummer: String(nummer).trim(), bezeichnung: bezeichnung || null });
+    } catch (err) {
+        if (/UNIQUE/.test(err.message)) {
+            return res.status(400).json({ error: 'VO mit dieser Nummer existiert bereits für diesen Anbieter' });
+        }
+        throw err;
+    }
+}));
+
+router.put('/:id', asyncHandler(async (req, res) => {
+    const { id } = req.params;
+    const { nummer, bezeichnung, aktiv } = req.body || {};
+    const current = await db.get('SELECT * FROM vos WHERE id = ?', [id]);
+    if (!current) return res.status(404).json({ error: 'VO nicht gefunden' });
+    const nextNummer = nummer !== undefined ? String(nummer).trim() : current.nummer;
+    if (!nextNummer) return res.status(400).json({ error: 'VO-Nummer darf nicht leer sein' });
+    try {
+        await db.run(
+            'UPDATE vos SET nummer = ?, bezeichnung = ?, aktiv = ? WHERE id = ?',
+            [
+                nextNummer,
+                bezeichnung !== undefined ? (bezeichnung ? String(bezeichnung).trim() : null) : current.bezeichnung,
+                aktiv !== undefined ? (aktiv ? 1 : 0) : current.aktiv,
+                id,
+            ]
+        );
+        res.json({ message: 'VO erfolgreich aktualisiert' });
+    } catch (err) {
+        if (/UNIQUE/.test(err.message)) {
+            return res.status(400).json({ error: 'VO mit dieser Nummer existiert bereits für diesen Anbieter' });
+        }
+        throw err;
+    }
+}));
+
+router.delete('/:id', asyncHandler(async (req, res) => {
+    const { id } = req.params;
+    // Prevent deletion if any tariff or schaltung references it.
+    const used = await db.get(
+        `SELECT
+            (SELECT COUNT(*) FROM tarife WHERE vo_id = ?) AS n_tarife,
+            (SELECT COUNT(*) FROM schaltungen WHERE vo_id = ?) AS n_schaltungen`,
+        [id, id]
+    );
+    if (used.n_tarife + used.n_schaltungen > 0) {
+        const parts = [];
+        if (used.n_tarife > 0) parts.push(`${used.n_tarife} Tarif(e)`);
+        if (used.n_schaltungen > 0) parts.push(`${used.n_schaltungen} Schaltung(en)`);
+        return res.status(400).json({ error: `VO kann nicht gelöscht werden: ${parts.join(', ')} verwenden diese VO` });
+    }
+    const result = await db.run('DELETE FROM vos WHERE id = ?', [id]);
+    if (result.changes === 0) return res.status(404).json({ error: 'VO nicht gefunden' });
+    res.json({ message: 'VO erfolgreich gelöscht' });
+}));
+
+module.exports = router;