release: promote Full baseline and prepare v2.5.0

[Arimacose]

Summary

• promote Full · HY-MT2 Q4 from Experimental to the shipping baseline across BuildConfig, provider profile, labels, notifications, attribution, User-Agent, docs, CI, and release asset names
• bump versionCode/versionName to 12 / 2.5.0
• bind v2.5.0 promotion to a feature-only, <=300-second signed-device acceptance schema covering the new Toasts, Full baseline identity, and zero target-app fatal events

Local verification

• 905 unit tests across Lite, Full, and Online: 0 failures/errors/skips
• lintLiteRelease lintFullRelease lintOnlineRelease
• generateReleaseSboms assembleOnlineContributor
• all three Release APK/AAB builds
• local Full release APK identity: com.screentranslation.app.full, 2.5.0-full, label 识屏翻译 Full · HY-MT2 Q4
• workflow YAML parse and git diff --check

Device boundary

No device operation is claimed by this PR. After merge, the signed acceptance Artifact from the exact main commit will be installed on Xiaomi 15 Pro for only the v2.5.0 Toast/Full-label checks and target-app fatal scan before release promotion.