Add kestrel purchase planner to community train

[CaptDany]

Summary

Adds Kestrel, a self-hosted purchase planner that calendarizes e-commerce purchases based on your paydays and budget.

Features

• Price Extraction: Paste any product URL — Kestrel auto-extracts title, price, and currency from Amazon, MercadoLibre, Aliexpress, IKEA, and Walmart
• Payday Scheduling: Configure monthly, biweekly, weekly, or custom payday schedules
• Budget Modes: Per-payday, flexible (base + bonuses), or total pool
• Smart Sorting: Sort items by price, priority, date added, or desired date
• Saving Mode: Large items automatically save across multiple pay cycles
• Optional Playwright Scraper: Sidecar container for JavaScript-heavy sites
• Self-Hosted: Single Go binary (~15MB), SQLite-backed, no external dependencies

Screenshots

Checklist

• App follows TrueNAS contribution guidelines
• app.yaml, item.yaml, ix_values.yaml, questions.yaml present
• Jinja2 docker-compose.yaml template using library v2.3.4
• Test values provided
• Screenshots

[CaptDany]

Updated the PR with the following fixes based on the contribution guidelines:

1. app.yaml: Fixed
   un_as_context\ format (user_name/group_name now use \Host user is [apps]\ / \Host group is [apps]\ per \generate_metadata.py\ output)
2. app.yaml: Added catalog URL to \sources\ list
3. questions.yaml: Added missing sections (
   un_as,
   etworks\ with container enum, \labels\ with container enum, \host_network, \certificate_id, \�dditional_envs,
   ead_only, \host_ips, SMB/NFS config)
4. docker-compose.yaml: Added \�dditional_envs\ loop
5. test_values/basic-values.yaml: Added \host_network, \certificate_id, \�dditional_envs; moved test port to 31012 (non-default)
6. ix_values.yaml: Switched to \ghcr.io/\ prefix