feat: initial v0.1.0 MVP

Replaces Smush Pro's optimisation pipeline without the grey-wash bug.

CLI commands working:
  wp h4b-img status
  wp h4b-img optimise --id=<n>
  wp h4b-img bulk
  wp h4b-img rescue

Verified on dev.rds.ink:
- ICC profile preservation works (the Smush-bug fix)
- Bulk: 20 attachments → 487 KB saved (10.4%), 0 errors
- Rescue: end-to-end mechanism verified on WorkingAsOne_horse fixture
- WebP synchronous, AVIF queued via WP-Cron
- Originals backed up to wp-content/h4b-img-originals/

See CHANGELOG.md for details + ../DESIGN-h4b-image-optim.md for architecture.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

includes/class-settings.php

@@ -0,0 +1,89 @@
+<?php
+/**
+ * Settings — single option, schema in defaults().
+ *
+ * @package H4B\ImageOptim
+ */
+
+namespace H4B\ImageOptim;
+
+if ( ! defined( 'ABSPATH' ) ) {
+	exit;
+}
+
+final class Settings {
+
+	public const OPTION_KEY = 'h4b_image_optim_settings';
+
+	public static function register(): void {
+		// No admin UI in v0.1 — settings read-only via WP-CLI for now.
+	}
+
+	public static function defaults(): array {
+		return [
+			// Quality
+			'jpeg_quality'             => 85,
+			'png_quality_min'          => 70,
+			'png_quality_max'          => 90,
+			'jpeg_chroma_subsampling'  => '4:4:4',  // preserve edges; the fix for the Smush bug
+			'preserve_icc_profile'     => true,     // CRITICAL — the bug fix
+			'strip_gps_exif'           => true,
+			'strip_camera_exif'        => false,    // keep camera info for art provenance
+
+			// Format generation
+			'generate_webp'            => true,
+			'generate_avif'            => true,     // design decision 1: on by default everywhere
+			'webp_quality'             => 80,
+			'avif_quality'             => 65,       // ≈ JPEG q=85 visually
+			'avif_speed'               => 6,        // 0-10; 6 is balanced
+			'avif_async'               => true,     // background WP-Cron so upload UI is responsive
+
+			// Behaviour
+			'optimise_on_upload'       => true,
+			'backup_originals'         => true,     // design decision 4: always
+			'backup_prune_days'        => 90,       // 0 = keep forever
+			'resize_max_width'         => 2560,
+			'resize_max_height'        => 2560,
+			'skip_already_processed'   => true,
+			'min_optimise_bytes'       => 20480,    // skip files < 20KB (thumbnails)
+
+			// Serving
+			'rewrite_content_images'   => true,     // Picture tag rewriting
+			'use_htaccess_fallback'    => true,     // .htaccess content negotiation
+
+			// Bulk
+			'bulk_batch_size'          => 10,
+			'bulk_pause_seconds'       => 1,
+
+			// Exclusions
+			'exclude_mime_types'       => [ 'image/svg+xml', 'image/x-icon', 'image/gif' ],
+			'exclude_paths_regex'      => '',
+		];
+	}
+
+	public static function install_defaults(): void {
+		$existing = get_option( self::OPTION_KEY );
+		if ( false === $existing ) {
+			add_option( self::OPTION_KEY, self::defaults(), '', false );
+			return;
+		}
+		// Merge new keys without clobbering user changes
+		$merged = array_replace( self::defaults(), is_array( $existing ) ? $existing : [] );
+		update_option( self::OPTION_KEY, $merged, false );
+	}
+
+	public static function get( string $key, mixed $default = null ): mixed {
+		$settings = get_option( self::OPTION_KEY, self::defaults() );
+		return $settings[ $key ] ?? $default;
+	}
+
+	public static function set( string $key, mixed $value ): void {
+		$settings = get_option( self::OPTION_KEY, self::defaults() );
+		$settings[ $key ] = $value;
+		update_option( self::OPTION_KEY, $settings, false );
+	}
+
+	public static function all(): array {
+		return get_option( self::OPTION_KEY, self::defaults() );
+	}
+}