Allow setting of favourite serp easter egg logo

[mikescamell]

Task/Issue URL: https://app.asana.com/1/137249556945/project/1207908166761516/task/1212553599261552?focus=true

Description

This PR adds the ability for users to set a SERP Easter Egg logo as their favourite, which will then display on all DuckDuckGo search result pages.

Features implemented:

1. Feature toggle - Added remote feature toggle (serpEasterEggLogos.setFavourite) to control the favourite logo functionality
2. Favourite logo data store - Added FavouriteSerpLogoDataStore to persist the user's favourite logo URL preference
3. Discovery screen enhancements - Updated the Easter Egg logo screen to:
   - Display a title telling the user they've discovered an Easter Egg logo
   - Added a button to set/unset the logo as favourite
4. Wiggle animation - Easter Egg logos now play a subtle wiggle animation when displayed in the omnibar:
   - Only plays once per unique logo URL
   - Skips animation for favourite logos
   - Waits for image crossfade to complete before animating
5. State management fixes - Fixed race conditions that could cause Easter Egg logos to be lost:
   - Preserve existing Easter Egg when onViewModeChanged is called
   - Distinguish between SerpLogo.Normal (explicitly no Easter Egg) and null (pending state)
   - Reset to Dax logo when favourite preference changes

Steps to test this PR

Easter Egg Discovery

• Search for a term that triggers an Easter Egg logo (e.g., "Southampton FC", "f1", "predator")
• Verify the Easter Egg logo appears in the omnibar with a wiggle animation
• Tap on the logo to open the enlarged view
• Verify the discovery text "You found a hidden logo!" is displayed at the top
• Verify the "Switch to This Logo" button is visible
• Tap anywhere outside to dismiss the view
• Search for another easter egg e.g. "hydra" and anticipate the wiggle animation
• As the wiggle animation plays click the logo
• The easter egg logo enlarged view should open and the logo should transition with no glitches
• Tap anywhere outside to dismiss the view
• The easter egg logo enlarged view should should transition back to the address with no glitches

Setting a Favourite Logo

• Tap on the logo to open the enlarged view
• Open the Easter Egg logo screen
• Tap "Switch to This Logo"
• Tap anywhere outside to dismiss the view
• Search for something that does not have an easter egg logo e.g. "fpl"
• Verify the favourite logo persists in the omnibar
• Search for a term that triggers an Easter Egg logo (e.g., "Southampton FC", "f1", "predator") but is not your current favourite logo
• Verify the favourite logo persists in the omnibar
• Search for the same term for your favourite logo
• Verify the logo no longer plays the wiggle animation (since it's now a favourite)

Resetting to Default

• With a favourite logo set, tap on the logo
• Verify the button now shows "Reset to Default"
• Tap "Reset Search Logo"
• Dismiss the easter egg logo screen
• Verify the DDG logo is visible
• Search for something that does not have an easter egg logo e.g. "fpl"
• Verify the DDG logo is still visible
• Search for a term that triggers an Easter Egg logo (e.g., "Southampton FC", "f1", "predator")
• Verify the Easter Egg logo appears in the omnibar with a wiggle animation

Flag off

Index: serp-logos/serp-logos-api/src/main/kotlin/com/duckduckgo/serp/logos/api/SerpEasterEggLogosToggles.kt
IDEA additional info:
Subsystem: com.intellij.openapi.diff.impl.patch.CharsetEP
<+>UTF-8
===================================================================
diff --git a/serp-logos/serp-logos-api/src/main/kotlin/com/duckduckgo/serp/logos/api/SerpEasterEggLogosToggles.kt b/serp-logos/serp-logos-api/src/main/kotlin/com/duckduckgo/serp/logos/api/SerpEasterEggLogosToggles.kt
--- a/serp-logos/serp-logos-api/src/main/kotlin/com/duckduckgo/serp/logos/api/SerpEasterEggLogosToggles.kt	(revision 2a9b098666ba9cd103cbe20e24fa7ff018cf7168)
+++ b/serp-logos/serp-logos-api/src/main/kotlin/com/duckduckgo/serp/logos/api/SerpEasterEggLogosToggles.kt	(date 1769694204288)
@@ -24,6 +24,6 @@
   @Toggle.DefaultValue(DefaultFeatureValue.FALSE)
   fun self(): Toggle

-    @Toggle.DefaultValue(DefaultFeatureValue.TRUE)
+    @Toggle.DefaultValue(DefaultFeatureValue.FALSE)
   fun setFavourite(): Toggle
}

• Set the logo you just searched for as a favourite
• Apply the patch above
• Install the app
• You should see the logo you set as favourite if you did not navigate away before re-installation
• Search for a term that triggers an Easter Egg logo (e.g., "Southampton FC", "f1", "predator")
• The new easter egg logo should show and should not be your favourite (flag off means no favourite so user's don't get stuck with it if we need to turn off the flag)
• Tap the EasterEgg logo
• The Easter Egg Logo screen should open
• Verify the discovery text "You found a hidden logo!" is displayed
• Verify the "Switch to This Logo" button is not visible
• Dismiss the easter egg logo screen
• Search for something that does not have an easter egg logo e.g. "fpl"
• The DDG logo should show
• Navigate to a website e.g. ign.com
• The green shield should be visible
• General smoke test, do searches in SERP with easter eggs, do non easter egg searches, navigate away to websites.
• Favourite logo set before turning the flag off does not show

UI changes

Before	After

---

Note

Medium Risk
Moderate risk: adds new persisted preference (DataStore), new UI state/animation paths, and changes SERP logo selection logic in BrowserTabViewModel/omnibar rendering, which could cause regressions in address-bar icon state or transitions.

Overview
Adds a new “favourite SERP Easter Egg logo” capability: users can set/unset a discovered Easter Egg logo, persist the chosen logo URL via a new DataStore, and have that logo override normal SERP logo extraction on DuckDuckGo search result pages when the serpEasterEggLogos.setFavourite toggle is enabled.

Updates the Easter Egg logo discovery screen to show discovery text and a favourite toggle button, introduces a one-time “wiggle” animation for non-favourite Easter Egg logos in the omnibar, and adds explicit cancellation of the logo animation when launching the logo screen to avoid transition glitches. Tests are expanded across BrowserTabViewModel, OmnibarLayoutViewModel, and serp-logos to cover toggle/favourite interactions and state preservation.

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