chore: point repo links at Flow-Tube/Flow

[A-EDev]

Summary

• The in-app update check now asks Flow-Tube/Flow for stable and nightly releases.
• About (phone and TV), changelog, crash report and release-note links point at the new repo, and the website link points at flow-tube.org.
• README, CONTRIBUTING, SECURITY, FUNDING and the issue template config use the new repo URLs.
• License headers in Kotlin files point at the new repo URL.

Related issue

Change type

• Bug fix
• Feature
• Refactor or maintenance
• Build, packaging, or CI
• Documentation

Validation

• ./gradlew :app:assembleGithubDebug
• ./gradlew :app:testGithubDebugUnitTest: 3738 tests, 0 failures
• I ran any additional flavor-specific build or test tasks affected by this change.
• I manually tested the affected behavior on an Android device or emulator.

Also ran ./gradlew spotlessCheck (passes) and :app:compileGithubDebugKotlin :app:compileFossDebugKotlin (both pass).

Test device and Android version:

Screenshots or recordings

Risk and compatibility

Installed builds keep checking the old A-EDev/Flow API URL and rely on GitHub's redirect. The first nightly from this merge should carry a run number above 1559.

• The change does not introduce secrets, private data, or unexpected telemetry.
• New user-facing text uses Android string resources.
• Dependency and lockfile changes are intentional and limited to this PR.
• Room schema changes include the required version bump and migration, or this PR does not change the Room schema.
• Breaking changes and upgrade steps are clearly documented.

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