fix(openrouter): respect the requesting user's saved model config

generatePostText ignored the userId it received and always read an
arbitrary row via getAnyOpenrouterConfig() (LIMIT 1, no ORDER BY),
so a model chosen and saved in Settings could be shadowed by another
stale config row. Now it prefers the requesting user's own config,
falling back to the most recently updated shared one. Also swap the
retired anthropic/claude-3.5-sonnet default for a live OpenRouter slug.

shared/schema.ts

@@ -127,7 +127,7 @@ export const openrouterConfig = pgTable("openrouter_config", {
   id: varchar("id").primaryKey().default(sql`gen_random_uuid()`),
   userId: varchar("user_id").notNull().unique().references(() => users.id, { onDelete: "cascade" }),
   apiKey: text("api_key").notNull(),
-  model: text("model").notNull().default("anthropic/claude-3.5-sonnet"),
+  model: text("model").notNull().default("anthropic/claude-sonnet-4.5"),
   systemPrompt: text("system_prompt").notNull().default("Tu es un expert en marketing des réseaux sociaux. Génère 3 variations de textes engageants pour des publications Facebook et Instagram à partir des informations produit fournies. Chaque variation doit être unique, captivante et optimisée pour l'engagement."),
   createdAt: timestamp("created_at").defaultNow(),
   updatedAt: timestamp("updated_at").defaultNow(),