refactor(backend): clean up jail service, add error handling service

- Extract jail status/processing to helper functions
- Add error_handling.py service for centralized error handling
- Update config.py with validation and defaults
- Update .env.example with all config options
- Remove obsolete Tasks.md, add Service-Development.md
- Minor fixes across routers and services

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Docs/CONFIGURATION.md

@@ -128,6 +128,18 @@ Per-IP rate limits applied to API endpoints.
 
 ---
 
+## Pagination & Display Limits
+
+Configurable limits that affect API response sizes and data retention.
+
+| Variable | Type | Default | Description |
+|----------|------|---------|-------------|
+| `BANGUI_MAX_PAGE_SIZE` | int | `500` | Maximum records returned per paginated API response. Individual endpoints may further limit this. Must be 1–10000. |
+| `BANGUI_PREVIEW_MAX_LINES` | int | `100` | Maximum IP lines returned in a blocklist source preview. Must be ≥ 1. |
+| `BANGUI_HISTORY_RETENTION_DAYS` | int | `90` | Number of days historical ban records are retained before archival cleanup. Must be ≥ 1. |
+
+---
+
 ## Observability
 
 | Variable | Type | Default | Description |