Rate limit account authentication attempts

SovereignAI-Starter/app/database.py

@@ -71,6 +71,14 @@ def initialize_database() -> None:
             CREATE INDEX IF NOT EXISTS idx_auth_sessions_user
                 ON auth_sessions(user_id, expires_at);
 
+            CREATE TABLE IF NOT EXISTS auth_rate_limits (
+                scope TEXT NOT NULL,
+                fingerprint TEXT NOT NULL,
+                window_started_at INTEGER NOT NULL,
+                attempts INTEGER NOT NULL CHECK(attempts >= 0),
+                PRIMARY KEY(scope, fingerprint)
+            );
+
             CREATE TABLE IF NOT EXISTS conversations (
                 id TEXT PRIMARY KEY,
                 user_id TEXT NOT NULL REFERENCES users(id) ON DELETE CASCADE,