refactor(astrolabe): replace client-side PDF.js with server-side PyMuPDF rendering

Replace the client-side PDF.js viewer with server-side rendering using PyMuPDF.
This avoids CSP worker restrictions and ES private field access issues that
affected Chromium browsers.

Changes:
- Add /api/v1/pdf-preview endpoint to MCP server (management.py)
- Add pdf-preview route and controller action in Astrolabe PHP backend
- Refactor PDFViewer.vue to display server-rendered PNG images
- Remove pdfjs-dist dependency and client-side PDF loading code
- Use @nextcloud/axios for CSRF token handling in PDFViewer

The server downloads the PDF via WebDAV, renders the requested page with
PyMuPDF at the specified scale, and returns a base64-encoded PNG image.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

third_party/astrolabe/vite.config.js

@@ -1,40 +1,7 @@
 import { defineConfig } from 'vite'
 import vue from '@vitejs/plugin-vue'
 import { resolve } from 'path'
-import { readFileSync, copyFileSync, writeFileSync, mkdirSync } from 'fs'
-
-// Plugin to copy PDF.js files to output directory
-// Both pdf.mjs and pdf.worker.mjs are loaded externally to avoid Vite transforming
-// ES private fields, which breaks compatibility with the fake worker fallback
-function copyPdfFiles() {
-  return {
-    name: 'copy-pdf-files',
-    writeBundle() {
-      mkdirSync(resolve(__dirname, 'js'), { recursive: true })
-      // Copy main library
-      copyFileSync(
-        resolve(__dirname, 'node_modules/pdfjs-dist/build/pdf.mjs'),
-        resolve(__dirname, 'js/pdf.mjs')
-      )
-      console.log('Copied pdf.mjs to js/')
-      // Copy worker (loaded by pdfjs at runtime)
-      copyFileSync(
-        resolve(__dirname, 'node_modules/pdfjs-dist/build/pdf.worker.mjs'),
-        resolve(__dirname, 'js/pdf.worker.mjs')
-      )
-      console.log('Copied pdf.worker.mjs to js/')
-      // Create loader script that imports pdf.mjs and sets window.pdfjsLib
-      // This is loaded via script tag before the main app
-      const loaderScript = `// PDF.js loader - imports pdf.mjs and exposes it globally
-// Loaded before main app to make pdfjsLib available as window.pdfjsLib
-import * as pdfjsLib from './pdf.mjs';
-window.pdfjsLib = pdfjsLib;
-`
-      writeFileSync(resolve(__dirname, 'js/pdfjs-loader.mjs'), loaderScript)
-      console.log('Created pdfjs-loader.mjs in js/')
-    }
-  }
-}
+import { readFileSync } from 'fs'
 
 // Read app info from info.xml for @nextcloud/vue
 const infoXml = readFileSync(resolve(__dirname, 'appinfo/info.xml'), 'utf-8')
@@ -42,7 +9,7 @@ const appName = infoXml.match(/<id>([^<]+)<\/id>/)?.[1] || 'astrolabe'
 const appVersion = infoXml.match(/<version>([^<]+)<\/version>/)?.[1] || ''
 
 export default defineConfig({
-  plugins: [vue(), copyPdfFiles()],
+  plugins: [vue()],
   define: {
     appName: JSON.stringify(appName),
     appVersion: JSON.stringify(appVersion),