feat: auto-save drafts + publish step for viewers

Editors' changes are now auto-saved (5 s after the last edit, at most
30 s after the first unsaved one, retried on failure) with a status
indicator; leaving the page with unsaved changes prompts a warning.

Each schedule file keeps a published snapshot next to the draft.
Viewer/cis roles load and export only the published snapshot; the
editor's draft becomes visible to them only after "Publikovat".
Toolbar shows the publish state ("Nepublikované změny" / "Publikováno
HH:MM"), the file manager shows the publish date, and viewers pick up a
new publish automatically within a minute.

Server: GET /api/files/:id?view=published, POST /api/files/:id/publish,
?view=published on all exports, one-time migration that seeds the
published snapshot from the current data on startup.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

web/server.js

@@ -46,12 +46,7 @@ function listScheduleFiles() {
   for (const f of files) {
     try {
       const raw = JSON.parse(readFileSync(join(SCHEDULES_DIR, f), 'utf-8'))
-      result.push({
-        id: raw.id,
-        name: raw.name,
-        createdAt: raw.createdAt,
-        modifiedAt: raw.modifiedAt,
-      })
+      result.push(fileMeta(raw))
     } catch {}
   }
   result.sort((a, b) => new Date(b.modifiedAt) - new Date(a.modifiedAt))
@@ -69,6 +64,41 @@ function saveScheduleFile(fileObj) {
   writeFileSync(join(SCHEDULES_DIR, `${fileObj.id}.json`), JSON.stringify(fileObj, null, 2), 'utf-8')
 }
 
+// --- Draft vs. published ---
+// file.data      = working copy (editor's draft, auto-saved)
+// file.published = snapshot viewers see; updated only by POST /api/files/:id/publish
+
+function ensurePublished(file) {
+  // Files created before publishing existed: their current data becomes the published snapshot
+  if (!file.published) {
+    file.published = JSON.parse(JSON.stringify(file.data))
+    file.publishedAt = file.modifiedAt || new Date().toISOString()
+    return true
+  }
+  return false
+}
+
+function hasUnpublishedChanges(file) {
+  if (!file.published) return true
+  return JSON.stringify(file.data) !== JSON.stringify(file.published)
+}
+
+function fileMeta(file) {
+  return {
+    id: file.id,
+    name: file.name,
+    createdAt: file.createdAt,
+    modifiedAt: file.modifiedAt,
+    publishedAt: file.publishedAt ?? null,
+    hasUnpublishedChanges: hasUnpublishedChanges(file),
+  }
+}
+
+// Pick draft or published data for a request (?view=published)
+function pickData(file, view) {
+  return view === 'published' && file.published ? file.published : file.data
+}
+
 function getMostRecentFile() {
   const files = listScheduleFiles()
   return files.length > 0 ? files[0] : null
@@ -97,6 +127,15 @@ function migrateIfNeeded() {
 
 migrateIfNeeded()
 
+// Give every existing file a published snapshot (one-time, idempotent)
+for (const f of listScheduleFiles()) {
+  const file = loadScheduleFile(f.id)
+  if (file && ensurePublished(file)) {
+    saveScheduleFile(file)
+    console.log(`Published snapshot initialised for ${file.name} (${file.id})`)
+  }
+}
+
 // --- Diff computation ---
 
 function computeDiff(file1, file2) {
@@ -187,7 +226,8 @@ app.get('/api/files/:id', (req, res) => {
   try {
     const file = loadScheduleFile(req.params.id)
     if (!file) return res.status(404).json({ error: 'File not found' })
-    res.json(file)
+    const view = req.query.view === 'published' ? 'published' : 'draft'
+    res.json({ ...fileMeta(file), view, data: pickData(file, view) })
   } catch (err) {
     console.error('Error loading file:', err)
     res.status(500).json({ error: 'Failed to load file' })
@@ -207,7 +247,7 @@ app.get('/api/files/:id/export-excel', async (req, res) => {
   try { fileData = JSON.parse(readFileSync(filePath, 'utf8')) }
   catch { return res.status(500).json({ error: 'Failed to read file' }) }
 
-  const input = JSON.stringify({ schedule: fileData.data, month, year })
+  const input = JSON.stringify({ schedule: pickData(fileData, req.query.view), month, year })
   const scriptPath = join(__dirname, 'export_full_excel.py')
 
   try {
@@ -257,7 +297,7 @@ app.get('/api/files/:id/export-harmonogram', async (req, res) => {
   try { fileData = JSON.parse(readFileSync(filePath, 'utf8')) }
   catch { return res.status(500).json({ error: 'Failed to read file' }) }
 
-  const input = JSON.stringify({ schedule: fileData.data, month, year })
+  const input = JSON.stringify({ schedule: pickData(fileData, req.query.view), month, year })
   const scriptPath = join(__dirname, 'export_harmonogram.py')
 
   try {
@@ -306,7 +346,7 @@ app.get('/api/files/:id/export-dochazka', async (req, res) => {
   try { fileData = JSON.parse(readFileSync(filePath, 'utf8')) }
   catch { return res.status(500).json({ error: 'Failed to read file' }) }
 
-  const input = JSON.stringify({ schedule: fileData.data, month, year })
+  const input = JSON.stringify({ schedule: pickData(fileData, req.query.view), month, year })
   const scriptPath = join(__dirname, 'export_dochazka.py')
 
   try {
@@ -356,14 +396,11 @@ app.post('/api/files', (req, res) => {
       createdAt: now,
       modifiedAt: now,
       data,
+      published: JSON.parse(JSON.stringify(data)),
+      publishedAt: now,
     }
     saveScheduleFile(fileObj)
-    res.json({
-      id: fileObj.id,
-      name: fileObj.name,
-      createdAt: fileObj.createdAt,
-      modifiedAt: fileObj.modifiedAt,
-    })
+    res.json(fileMeta(fileObj))
   } catch (err) {
     console.error('Error creating file:', err)
     res.status(500).json({ error: 'Failed to create file' })
@@ -387,18 +424,40 @@ app.put('/api/files/:id', (req, res) => {
     file.modifiedAt = new Date().toISOString()
     saveScheduleFile(file)
 
-    res.json({
-      id: file.id,
-      name: file.name,
-      createdAt: file.createdAt,
-      modifiedAt: file.modifiedAt,
-    })
+    res.json(fileMeta(file))
   } catch (err) {
     console.error('Error updating file:', err)
     res.status(500).json({ error: 'Failed to update file' })
   }
 })
 
+// Publish: optionally save the given draft, then make it the version viewers see
+app.post('/api/files/:id/publish', (req, res) => {
+  try {
+    const file = loadScheduleFile(req.params.id)
+    if (!file) return res.status(404).json({ error: 'File not found' })
+
+    const now = new Date().toISOString()
+    const { data } = req.body || {}
+    if (data) {
+      if ((!data.people && !data.stations) || !data.dayIndex) {
+        return res.status(400).json({ error: 'Invalid schedule data (need people/stations and dayIndex)' })
+      }
+      file.data = data
+      file.modifiedAt = now
+    }
+    file.published = JSON.parse(JSON.stringify(file.data))
+    file.publishedAt = now
+    saveScheduleFile(file)
+    console.log(`Published ${file.name} (${file.id}) at ${now}`)
+
+    res.json(fileMeta(file))
+  } catch (err) {
+    console.error('Error publishing file:', err)
+    res.status(500).json({ error: 'Failed to publish file' })
+  }
+})
+
 // Delete file
 app.delete('/api/files/:id', (req, res) => {
   try {