feat: Implement advanced foil effects with rolling rainbow, circular glare, and mobile entrance animations, alongside a fix for foil rendering on non-foil cards.

docs/development/devlog/2025-12-17-020000_pro_foil_implementation.md

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+# Pro Foil Implementation
+
+## Objective
+Implement a high-fidelity "Pro" foil effect using generic CSS techniques inspired by community "Holo" styles, creating a sophisticated rainbow and texture mapping.
+
+## Changes
+- **CSS Class `foil-holo`**:
+    - Added to `src/client/src/styles/main.css`.
+    - This class builds a complex multi-layered background image stack:
+        - **Layer 1**: Vertical Repeating Rainbow (`0deg` linear gradient).
+        - **Layer 2**: Diagonal Texture (`133deg` repeating linear gradient with hard-light/hue stops).
+    - Uses `background-blend-mode: screen, hue` to mix these layers dynamically.
+    - Uses `mix-blend-mode: color-dodge` to composite onto the card image.
+    - Includes a custom animation `foil-shift` (15s linear infinite) that shifts the background position vertically and diagonally, creating an "always active" shimmering effect.
+- **CardPreview Update**:
+    - Updated `FoilOverlay` to use the `.foil-holo` class.
+    - Retained the **Gaussian Circular Glare** (`radial-gradient` + `animate-spin-slow`) as a top-layer "spotlight" effect.
+
+## Result
+The foil effect is now significantly more intricate, featuring vertical color bands and diagonal textures that shift over time, mimicking the look of high-end TCG holofoils (like "Secret Rares" or "Full Arts").