feat(observability): implement global database error logging, Prometheus error metrics, and max 3-panel Grafana dashboard

db/database.py

@@ -71,6 +71,19 @@ CREATE TABLE IF NOT EXISTS settings (
     description TEXT
 );
 
+CREATE TABLE IF NOT EXISTS error_logs (
+    id BIGSERIAL PRIMARY KEY,
+    service_name VARCHAR(64) NOT NULL,
+    error_type VARCHAR(128) NOT NULL,
+    error_message TEXT NOT NULL,
+    traceback TEXT,
+    context JSONB DEFAULT '{}'::jsonb,
+    created_at TIMESTAMPTZ DEFAULT CURRENT_TIMESTAMP
+);
+
+CREATE INDEX IF NOT EXISTS idx_error_logs_created_at ON error_logs(created_at DESC);
+CREATE INDEX IF NOT EXISTS idx_error_logs_service ON error_logs(service_name);
+
 -- Migration safety for existing tables
 ALTER TABLE targets ADD COLUMN IF NOT EXISTS personality TEXT DEFAULT '';
 ALTER TABLE targets ADD COLUMN IF NOT EXISTS custom_footer TEXT DEFAULT '';