feat: add long-press contextual actions on post cards

Long press any post card to open a context menu with state-aware actions:
- Copy text (all states)
- ERROR: Retry now, Edit & retry, View error message
- QUEUE: Edit, Reschedule (native DateTimePicker → PUT /posts/:id)
- PUBLISHED: Repost
- DRAFT: Edit & schedule

Compose screen now accepts prefillContent/prefillIntegrationIds router
params to pre-fill content and channel selection when editing or reposting.
Adds expo-clipboard for clipboard support.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

artifacts/postiz-mobile/app/(tabs)/compose.tsx

@@ -5,7 +5,8 @@ import * as Haptics from "expo-haptics";
 import { Image } from "expo-image";
 import * as ImagePicker from "expo-image-picker";
 import { fetch as expoFetch } from "expo/fetch";
-import React, { useState } from "react";
+import { useLocalSearchParams } from "expo-router";
+import React, { useEffect, useState } from "react";
 import {
   ActivityIndicator,
   Alert,
@@ -29,6 +30,10 @@ export default function ComposeScreen() {
   const insets = useSafeAreaInsets();
   const { client, isConfigured, apiKey, baseUrl } = usePostiz();
   const queryClient = useQueryClient();
+  const { prefillContent, prefillIntegrationIds } = useLocalSearchParams<{
+    prefillContent?: string;
+    prefillIntegrationIds?: string;
+  }>();
   const [content, setContent] = useState("");
   const [selectedChannels, setSelectedChannels] = useState<string[]>([]);
   const [postNow, setPostNow] = useState(false);
@@ -41,6 +46,13 @@ export default function ComposeScreen() {
   const [uploading, setUploading] = useState(false);
   const [submitting, setSubmitting] = useState(false);
 
+  useEffect(() => {
+    if (prefillContent) setContent(String(prefillContent));
+    if (prefillIntegrationIds) {
+      setSelectedChannels(String(prefillIntegrationIds).split(",").filter(Boolean));
+    }
+  }, [prefillContent, prefillIntegrationIds]);
+
   const { data: integrations, isLoading: loadingIntegrations } =
     useQuery<PostizIntegration[]>({
       queryKey: ["integrations", !!client],