feat: UX improvements, security hardening, and code cleanup

- Extract shared extractError utility (lib/extractError.ts), remove 3 duplicate copies
- Export DEFAULT_BASE_URL from PostizContext, remove duplicate in settings
- Add 401 interceptor in axios client: fires UnauthorizedHandler in _layout → alert + redirect to Settings
- Calendar day items now tappable: tap opens context menu (Copy / Edit / Repost)
- Persist sort order (newest/oldest) across sessions via AsyncStorage
- Filter chips show post count per status (Queue 3, Error 1, etc.)
- Copy text action now shows a brief "Copied" toast + haptic feedback
- PostCard: swipe right → Reschedule action (QUEUE posts only, amber color)
- Compose: per-network char limit (Twitter 280, Instagram 2200…) with color warning at 90%
- Compose: local draft save/restore via AsyncStorage with restore banner on open
- Compose: prefillImagePath/prefillImageId params allow Edit/Repost to carry over existing media

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

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

@@ -1,10 +1,12 @@
 import { Feather } from "@expo/vector-icons";
 import { useQuery } from "@tanstack/react-query";
-import axios from "axios";
+import * as Clipboard from "expo-clipboard";
+import * as Haptics from "expo-haptics";
 import { router } from "expo-router";
 import React, { useMemo, useState } from "react";
 import {
   ActivityIndicator,
+  Alert,
   FlatList,
   Platform,
   StyleSheet,
@@ -17,24 +19,7 @@ import { useSafeAreaInsets } from "react-native-safe-area-context";
 import { PostizPost, usePostiz } from "@/context/PostizContext";
 import { useColors } from "@/hooks/useColors";
 import { StatusBadge } from "@/components/StatusBadge";
-
-function extractError(err: unknown): string {
-  if (axios.isAxiosError(err)) {
-    const status = err.response?.status;
-    const data = err.response?.data;
-    if (data) {
-      const body =
-        typeof data === "string"
-          ? data.slice(0, 200)
-          : (data?.message ?? data?.error ?? JSON.stringify(data)).toString().slice(0, 200);
-      return status ? `HTTP ${status}: ${body}` : body;
-    }
-    if (status) return `HTTP ${status} — ${err.message}`;
-    if (err.message) return err.message;
-  }
-  if (err instanceof Error) return err.message;
-  return "Unknown error";
-}
+import { extractError } from "@/lib/extractError";
 
 function formatDate(date: Date): string {
   const y = date.getFullYear();
@@ -65,6 +50,39 @@ export default function CalendarScreen() {
   const insets = useSafeAreaInsets();
   const { client, isConfigured } = usePostiz();
 
+  const showContextMenu = (post: PostizPost) => {
+    Haptics.impactAsync(Haptics.ImpactFeedbackStyle.Medium);
+    const preview = post.content.slice(0, 60) + (post.content.length > 60 ? "…" : "");
+    const integrations = post.integrations ?? (post.integration ? [post.integration] : []);
+    Alert.alert(
+      post.state === "PUBLISHED" ? "Published post" :
+      post.state === "QUEUE" ? "Scheduled post" :
+      post.state === "ERROR" ? "Failed post" : "Draft",
+      preview,
+      [
+        {
+          text: "Copy text",
+          onPress: () => {
+            Clipboard.setStringAsync(post.content);
+            Haptics.notificationAsync(Haptics.NotificationFeedbackType.Success);
+          },
+        },
+        {
+          text: post.state === "PUBLISHED" ? "Repost" : "Edit",
+          onPress: () =>
+            router.push({
+              pathname: "/(tabs)/compose",
+              params: {
+                prefillContent: post.content,
+                prefillIntegrationIds: integrations.map((i) => i.id).join(","),
+              },
+            }),
+        },
+        { text: "Cancel", style: "cancel" },
+      ]
+    );
+  };
+
   const now = new Date();
   const [currentMonth, setCurrentMonth] = useState({
     year: now.getFullYear(),
@@ -255,6 +273,7 @@ export default function CalendarScreen() {
             <TouchableOpacity
               style={[styles.dayPost, { borderBottomColor: colors.border }]}
               activeOpacity={0.7}
+              onPress={() => showContextMenu(item)}
             >
               <View style={styles.dayPostLeft}>
                 <Text style={[styles.timeText, { color: colors.primary }]}>