Enable R8 optimization

[joshliebe]

Task/Issue URL: https://app.asana.com/1/137249556945/project/1200204095367872/task/1218149406979969?focus=true
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Description

• Removes -dontoptimize by using getDefaultProguardFile('proguard-android-optimize.txt') for release builds.
• Requires Enable R8 for internal builds #9664

Steps to test this PR

• General smoke test
• Smoke test sync
• Smoke test PIR
• Smoke test autofill
• Smoke test VPN
• Smoke test Duck.ai
• Smoke test downloads
• Smoke test crash reporting

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Note

Low Risk
Single Gradle default-rules swap with release minification still disabled; main risk is unexpected shrink/obfuscation behavior when minify is later enabled without sufficient keep rules.

Overview
The release build type in app/build.gradle now points proguardFiles at proguard-android-optimize.txt instead of proguard-android.txt, matching the pattern already used in gradle/android-library.gradle.

That default ruleset turns on additional R8 shrinking and optimization beyond the non-optimize file. minifyEnabled is still false for release in this diff, so the new rules only affect builds once release minification/R8 is actually enabled (or if another flag turns it on elsewhere).

^{Reviewed by Cursor Bugbot for commit 3830ce1. Bugbot is set up for automated code reviews on this repo. Configure here.}

[joshliebe]

• Enable R8 optimization #9716 👈 (View in Graphite)
• develop

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