feat: mandatory auto-generated passwords for share links + admin password copy/regeneration + password gate rate limiting

app/storage/schema.sql

@@ -199,6 +199,7 @@ CREATE TABLE IF NOT EXISTS share_links (
     slug TEXT NOT NULL UNIQUE,
     objet_restriction TEXT,
     password_hash TEXT,
+    encrypted_password TEXT,
     is_active INTEGER NOT NULL DEFAULT 1,
     usage_count INTEGER NOT NULL DEFAULT 0,
     created_by INTEGER NOT NULL,