v0.1.17: UI fixes, Linux improvements, documentation overhaul

UI/UX:
- Fix heartbeat auto-refresh and rate-limiting page
- Add navigation breadcrumbs to settings pages
- New screenshots added

Linux Agent v0.1.17:
- Fix disk detection for multiple mount points
- Improve installer idempotency
- Prevent duplicate registrations

Documentation:
- README rewrite: 538→229 lines, homelab-focused
- Split docs: API.md, CONFIGURATION.md, DEVELOPMENT.md
- Add NOTICE for Apache 2.0 attribution

aggregator-server/internal/database/migrations/012_create_admin_user.up.sql

@@ -0,0 +1,10 @@
+-- Create admin user from environment configuration
+-- This migration reads the admin credentials from environment variables
+-- and creates the initial admin user in the database
+
+-- Note: This is a placeholder migration that will be executed by the application
+-- The actual user creation logic is handled in the main application startup
+-- to allow for proper password hashing and error handling
+
+-- The admin user creation is handled by the application during startup
+-- This migration file exists for version tracking purposes