Add announcement table to database for storing important information

Implement database migration scripts and SQL to create the 'announcements' table with relevant columns, constraints, and indexes. Also, adjust frontend component logic for handling 'all' store selection.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: e437ffed-c31b-44eb-9fd5-b6f9faa8e7ce
Replit-Commit-Checkpoint-Type: full_checkpoint
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/1957c339-2757-4d1f-8e92-e9f71a1ce58e/e437ffed-c31b-44eb-9fd5-b6f9faa8e7ce/biGr9ER

client/src/components/AnnouncementCard.tsx

@@ -212,14 +212,14 @@ export default function AnnouncementCard() {
                     render={({ field }) => (
                       <FormItem>
                         <FormLabel>Magasin (optionnel)</FormLabel>
-                        <Select onValueChange={(value) => field.onChange(value ? parseInt(value) : undefined)}>
+                        <Select onValueChange={(value) => field.onChange(value === 'all' ? undefined : parseInt(value))}>
                           <FormControl>
                             <SelectTrigger>
                               <SelectValue placeholder="Tous les magasins" />
                             </SelectTrigger>
                           </FormControl>
                           <SelectContent>
-                            <SelectItem value="">Tous les magasins</SelectItem>
+                            <SelectItem value="all">Tous les magasins</SelectItem>
                             {groups.map((group: any) => (
                               <SelectItem key={group.id} value={group.id.toString()}>
                                 {group.name}