feat: implement comprehensive retry mechanism and improve observability

Add retry tracking to scrape jobs with configurable max retries (default 5), implement
automatic database migrations on startup, and significantly reduce logging noise from
infrastructure layers. Enhanced tracing with structured spans for better debugging while
keeping output readable by suppressing verbose trace logs from rate limiters and session
management. Improved error handling with detailed retry context and proper session cookie
validation.

migrations/20251103093649_add_retry_tracking.sql

@@ -0,0 +1,3 @@
+-- Add retry tracking columns to scrape_jobs table
+ALTER TABLE scrape_jobs ADD COLUMN retry_count INTEGER NOT NULL DEFAULT 0 CHECK (retry_count >= 0);
+ALTER TABLE scrape_jobs ADD COLUMN max_retries INTEGER NOT NULL DEFAULT 5 CHECK (max_retries >= 0);