feat: add reusable gallery carousel and ranking feed infrastructure

config/ranking.php

@@ -0,0 +1,63 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * Ranking system configuration — Skinbase Nova rank_v1
+ *
+ * All weights, half-lives, and thresholds are tunable here.
+ * Increment model_version when changing weights so caches expire gracefully.
+ */
+return [
+
+    // ── Model versioning ────────────────────────────────────────────────────
+    'model_version' => 'rank_v1',
+
+    // ── Engagement signal weights (log-scaled) ──────────────────────────────
+    'weights' => [
+        'views'      => 1.0,
+        'favourites' => 3.0,
+        'downloads'  => 2.5,
+    ],
+
+    // ── Time-decay half-lives (hours) ───────────────────────────────────────
+    'half_life' => [
+        'trending'  => 72,   // Explore / global trending
+        'new_hot'   => 36,   // New & Hot novelty feed
+        'best'      => 720,  // Evergreen / Best-of (30 days)
+        'category'  => 96,   // Per-category trending
+    ],
+
+    // ── Novelty boost (New & Hot only) ──────────────────────────────────────
+    'novelty_weight' => 0.35,
+
+    // ── Quality modifiers ───────────────────────────────────────────────────
+    'quality' => [
+        'has_tags'       => 0.05,
+        'has_thumbnail'  => 0.02,
+        'tag_count_max'  => 10,
+        'tag_count_bonus' => 0.01,  // per normalised tag fraction (max 0.01 total)
+        'penalty_hidden' => 0.50,   // deducted if hidden/inactive
+    ],
+
+    // ── Diversity constraints ────────────────────────────────────────────────
+    'diversity' => [
+        'max_per_author' => 3,
+        'list_size'      => 50,
+        'candidate_pool' => 200,  // top N candidates to run diversity filter on
+    ],
+
+    // ── Anti-spam / burst-view damping ──────────────────────────────────────
+    'spam' => [
+        'views_24h_threshold'     => 2000,
+        'fav_ratio_threshold'     => 0.002,
+        'dl_ratio_threshold'      => 0.001,
+        'trending_penalty_factor' => 0.5,
+    ],
+
+    // ── Redis cache ─────────────────────────────────────────────────────────
+    'cache' => [
+        'ttl'     => 900,     // seconds (15 min) — lists are rebuilt hourly
+        'prefix'  => 'rank',
+    ],
+];