fix(openrouter): trim API key and guard against empty key

An OpenRouter key with trailing whitespace/newline (common from
copy-paste) produces "Missing Authentication header" from their API,
which looked identical to a missing key. Trim apiKey on save (schema
level) and on use (defense in depth), fail fast with a clear message
if the stored key is empty, and log a masked key preview + model on
each generation call to make future auth failures diagnosable from
container logs.

shared/schema.ts

@@ -394,7 +394,7 @@ export const insertOpenrouterConfigSchema = createInsertSchema(openrouterConfig)
   createdAt: true,
   updatedAt: true,
 }).extend({
-  apiKey: z.string().min(1, "La clé API ne peut pas être vide"),
+  apiKey: z.string().trim().min(1, "La clé API ne peut pas être vide"),
 });
 
 export const updateOpenrouterConfigSchema = insertOpenrouterConfigSchema.partial({