Remove system settings functionality and related database migrations

server/internal/db/migrations/postgres/001_initial_schema.up.sql

@@ -46,14 +46,6 @@ CREATE TABLE IF NOT EXISTS sessions (
     FOREIGN KEY (user_id) REFERENCES users (id) ON DELETE CASCADE
 );
 
--- Create system_settings table for application settings
-CREATE TABLE IF NOT EXISTS system_settings (
-    key TEXT PRIMARY KEY,
-    value TEXT NOT NULL,
-    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
-    updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
-);
-
 -- Create indexes for performance
 CREATE INDEX IF NOT EXISTS idx_sessions_user_id ON sessions(user_id);
 CREATE INDEX IF NOT EXISTS idx_sessions_expires_at ON sessions(expires_at);