Delete legacy code that used old company_ai_usage/job_seeker_ai_usage tables:
- Remove has_active_ai_pack() - old AI_PACK pricing package check
- Remove check_and_increment_usage() - legacy daily quota tracking
- Remove BASE_AI_LIMIT, get_ai_limit_for_package constants/functions
- Remove legacy queries from ai_auto_apply() and ai_usage_status()
- Update auto_apply.rs to use user_ai_subscriptions.daily_actions_used
instead of job_seeker_ai_usage table
- Inline apply_scheduled_downgrades() and expire_trials() in cron tasks
to remove dependency on users crate internal modules
The new system uses user_ai_subscriptions with:
- daily_actions_used / daily_credits_used counters
- monthly_credits_total / monthly_credits_used
- purchased_credits_total / purchased_credits_used
All AI billing now flows through the wallet/ledger system with
LiteLLM integration (Tasks 1-10).
- Add get_llm_base_url() and get_llm_model() helper functions
- Update call_ollama_inline to route to LiteLLM when LLM_PROVIDER=litellm
- Add auto-apply cron task for background job matching
- Auto-apply matches job seekers to new jobs based on skills
- Generate cover letters via LiteLLM for each application
