chore: remove obsolete Android app configuration files

- Deleted build.gradle.kts, gradle.properties, and gradlew files as part of the cleanup process.
- Removed local.properties and various generated files from the .gradle directory to streamline the project structure.
- Cleared out unnecessary build artifacts and intermediate files to improve project maintainability.

backend/controllers/billingController.js

@@ -0,0 +1,202 @@
+import fs from 'fs';
+import multer from 'multer';
+import path from 'path';
+import billingService from '../services/billingService.js';
+
+const storage = multer.diskStorage({
+  destination: (req, file, cb) => {
+    const dir = 'uploads/billing-templates';
+    fs.mkdirSync(dir, { recursive: true });
+    cb(null, dir);
+  },
+  filename: (req, file, cb) => {
+    const ext = path.extname(file.originalname) || '.pdf';
+    cb(null, `billing-template-${Date.now()}-${Math.round(Math.random() * 1e9)}${ext}`);
+  }
+});
+
+const upload = multer({
+  storage,
+  limits: { fileSize: 10 * 1024 * 1024 },
+  fileFilter: (req, file, cb) => {
+    const ext = path.extname(file.originalname || '').toLowerCase();
+    const isPdf = ext === '.pdf' || (file.mimetype || '').includes('pdf');
+    if (!isPdf) {
+      return cb(new Error('Nur PDF-Dateien sind erlaubt.'));
+    }
+    cb(null, true);
+  }
+});
+
+export const uploadBillingTemplateMiddleware = upload.single('templatePdf');
+
+export const listTemplates = async (req, res) => {
+  try {
+    const { authcode: userToken } = req.headers;
+    const { clubId } = req.params;
+    const result = await billingService.listTemplates(userToken, clubId);
+    res.status(result.status).json(result.response);
+  } catch (error) {
+    console.error('[listTemplates] Error:', error);
+    res.status(500).json({ success: false, error: 'Vorlagen konnten nicht geladen werden.' });
+  }
+};
+
+export const createTemplate = async (req, res) => {
+  try {
+    const { authcode: userToken } = req.headers;
+    const { clubId } = req.params;
+    const result = await billingService.createTemplate(userToken, clubId, req.body || {}, req.file);
+    res.status(result.status).json(result.response);
+  } catch (error) {
+    console.error('[createTemplate] Error:', error);
+    res.status(500).json({ success: false, error: 'Vorlage konnte nicht gespeichert werden.' });
+  }
+};
+
+export const deleteTemplate = async (req, res) => {
+  try {
+    const { authcode: userToken } = req.headers;
+    const { templateId } = req.params;
+    const result = await billingService.deleteTemplate(userToken, templateId);
+    res.status(result.status).json(result.response);
+  } catch (error) {
+    console.error('[deleteTemplate] Error:', error);
+    res.status(500).json({ success: false, error: 'Vorlage konnte nicht gelöscht werden.' });
+  }
+};
+
+export const updateTemplateFields = async (req, res) => {
+  try {
+    const { authcode: userToken } = req.headers;
+    const { templateId } = req.params;
+    const result = await billingService.saveTemplateFields(userToken, templateId, req.body?.fields || []);
+    res.status(result.status).json(result.response);
+  } catch (error) {
+    console.error('[updateTemplateFields] Error:', error);
+    res.status(500).json({ success: false, error: 'Felder konnten nicht gespeichert werden.' });
+  }
+};
+
+export const createRun = async (req, res) => {
+  try {
+    const { authcode: userToken } = req.headers;
+    const { clubId } = req.params;
+    const result = await billingService.createRun(userToken, clubId, req.body || {});
+    res.status(result.status).json(result.response);
+  } catch (error) {
+    console.error('[createRun] Error:', error);
+    res.status(500).json({ success: false, error: 'Abrechnungslauf konnte nicht erstellt werden.' });
+  }
+};
+
+export const listRuns = async (req, res) => {
+  try {
+    const { authcode: userToken } = req.headers;
+    const { clubId } = req.params;
+    const result = await billingService.listRuns(userToken, clubId);
+    res.status(result.status).json(result.response);
+  } catch (error) {
+    console.error('[listRuns] Error:', error);
+    res.status(500).json({ success: false, error: 'Abrechnungsläufe konnten nicht geladen werden.' });
+  }
+};
+
+export const getRunDetails = async (req, res) => {
+  try {
+    const { authcode: userToken } = req.headers;
+    const { runId } = req.params;
+    const result = await billingService.getRunDetails(userToken, runId);
+    res.status(result.status).json(result.response);
+  } catch (error) {
+    console.error('[getRunDetails] Error:', error);
+    res.status(500).json({ success: false, error: 'Abrechnungslauf konnte nicht geladen werden.' });
+  }
+};
+
+export const deleteRun = async (req, res) => {
+  try {
+    const { authcode: userToken } = req.headers;
+    const { runId } = req.params;
+    const result = await billingService.deleteRun(userToken, runId);
+    res.status(result.status).json(result.response);
+  } catch (error) {
+    console.error('[deleteRun] Error:', error);
+    res.status(500).json({ success: false, error: 'Abrechnung konnte nicht gelöscht werden.' });
+  }
+};
+
+export const getUserSettings = async (req, res) => {
+  try {
+    const { authcode: userToken } = req.headers;
+    const { clubId } = req.params;
+    const result = await billingService.getUserSettings(userToken, clubId);
+    res.status(result.status).json(result.response);
+  } catch (error) {
+    console.error('[getUserSettings] Error:', error);
+    res.status(500).json({ success: false, error: 'Einstellungen konnten nicht geladen werden.' });
+  }
+};
+
+export const calculateHoursPreview = async (req, res) => {
+  try {
+    const { authcode: userToken } = req.headers;
+    const { clubId } = req.params;
+    const { monthFrom, monthTo } = req.query;
+    const result = await billingService.calculateHoursPreview(userToken, clubId, monthFrom, monthTo);
+    res.status(result.status).json(result.response);
+  } catch (error) {
+    console.error('[calculateHoursPreview] Error:', error);
+    res.status(500).json({ success: false, error: 'Stunden konnten nicht berechnet werden.' });
+  }
+};
+
+export const generateRun = async (req, res) => {
+  try {
+    const { authcode: userToken } = req.headers;
+    const { runId } = req.params;
+    const result = await billingService.generateRun(userToken, runId, req.body || {});
+    res.status(result.status).json(result.response);
+  } catch (error) {
+    console.error('[generateRun] Error:', error);
+    const message = String(error?.message || '');
+    if (message.includes('Formularfelder') || message.includes('Feldnamen') || message.includes('Fehlend:')) {
+      return res.status(400).json({ success: false, error: message });
+    }
+    res.status(500).json({ success: false, error: 'Abrechnung konnte nicht erzeugt werden.' });
+  }
+};
+
+export const downloadTemplatePdf = async (req, res) => {
+  try {
+    const { authcode: userToken } = req.headers;
+    const { templateId } = req.params;
+    const result = await billingService.downloadTemplatePdf(userToken, templateId);
+    if (result.status !== 200) {
+      return res.status(result.status).json(result.response);
+    }
+    res.setHeader('Content-Disposition', `inline; filename="${result.file.name}"`);
+    res.setHeader('Content-Type', result.file.mimeType);
+    return res.sendFile(result.file.path);
+  } catch (error) {
+    console.error('[downloadTemplatePdf] Error:', error);
+    res.status(500).json({ success: false, error: 'PDF konnte nicht geladen werden.' });
+  }
+};
+
+export const downloadRunPdf = async (req, res) => {
+  try {
+    const { authcode: userToken } = req.headers;
+    const { runId } = req.params;
+    const result = await billingService.downloadGeneratedRunPdf(userToken, runId);
+    if (result.status !== 200) {
+      return res.status(result.status).json(result.response);
+    }
+    res.setHeader('Content-Disposition', `attachment; filename="${result.file.name}"`);
+    res.setHeader('Content-Type', result.file.mimeType);
+    return res.sendFile(result.file.path);
+  } catch (error) {
+    console.error('[downloadRunPdf] Error:', error);
+    res.status(500).json({ success: false, error: 'Abrechnungs-PDF konnte nicht geladen werden.' });
+  }
+};