feat(chat): preserve message drafts in session temp store

frontend/stores/temp.js

@@ -10,6 +10,71 @@ export const useTempStore = defineStore('temp', () => {
     const pages = ref({})
     const settings = ref({})
 
+    // Drafts stay local: temp_config is also returned in tenant profile lists.
+    const chatDrafts = ref({})
+    const sendingChatDrafts = ref({})
+    const loadedChatDrafts = new Set()
+    const draftStoragePrefix = 'fedeo:chat-draft:v1:'
+    const toast = useToast()
+    let draftStorageWarningShown = false
+
+    function getChatDraft(key) {
+        if (!loadedChatDrafts.has(key)) {
+            loadedChatDrafts.add(key)
+            try {
+                const saved = JSON.parse(sessionStorage.getItem(draftStoragePrefix + key) || 'null')
+                if (saved && typeof saved.text === 'string' && typeof saved.clientId === 'string'
+                    && saved.text.length <= 10000 && (!saved.image || (
+                        typeof saved.image.name === 'string' && typeof saved.image.dataUrl === 'string'
+                        && saved.image.dataUrl.length <= 480000
+                        && /^data:image\/(jpeg|png|webp);base64,[A-Za-z0-9+/=]+$/.test(saved.image.dataUrl)
+                    ))) chatDrafts.value[key] = saved
+            } catch { /* Disabled storage or an invalid entry must not block the chat. */ }
+        }
+        return chatDrafts.value[key] || null
+    }
+
+    function setChatDraft(key, draft) {
+        loadedChatDrafts.add(key)
+        if (draft) chatDrafts.value[key] = draft
+        else delete chatDrafts.value[key]
+        try {
+            if (draft) sessionStorage.setItem(draftStoragePrefix + key, JSON.stringify(draft))
+            else sessionStorage.removeItem(draftStoragePrefix + key)
+        } catch {
+            // Do not restore an older version after a failed storage update.
+            try { sessionStorage.removeItem(draftStoragePrefix + key) } catch {}
+            if (!draftStorageWarningShown) {
+                draftStorageWarningShown = true
+                toast.add({ title: 'Entwurf nur vorübergehend gespeichert', description: 'Der Browserspeicher ist voll oder gesperrt. Bis zum Neuladen bleibt dein Entwurf im Chat erhalten.', color: 'warning' })
+            }
+        }
+    }
+
+    function isChatDraftSending(key) {
+        return !!sendingChatDrafts.value[key]
+    }
+
+    function startChatDraftSend(key, clientId) {
+        sendingChatDrafts.value[key] = clientId
+    }
+
+    function finishChatDraftSend(key, clientId) {
+        if (sendingChatDrafts.value[key] === clientId) delete sendingChatDrafts.value[key]
+    }
+
+    watch(() => auth.user?.id || auth.user?.user_id, (user, previous) => {
+        if (!previous || user === previous) return
+        chatDrafts.value = {}
+        sendingChatDrafts.value = {}
+        loadedChatDrafts.clear()
+        try {
+            for (const key of Object.keys(sessionStorage)) {
+                if (key.startsWith(draftStoragePrefix)) sessionStorage.removeItem(key)
+            }
+        } catch { /* Storage may be unavailable. In-memory drafts are still cleared. */ }
+    }, { flush: 'sync' })
+
     const storeTempConfig = async () => {
         const config = {
             searchStrings: searchStrings.value,
@@ -92,6 +157,11 @@ export const useTempStore = defineStore('temp', () => {
     }
 
     return {
+        getChatDraft,
+        setChatDraft,
+        isChatDraftSending,
+        startChatDraftSend,
+        finishChatDraftSend,
         setStoredTempConfig,
         searchStrings,
         modifySearchString,