CI/CD overhaul: pipeline structure, FlatBuffers v25, multi-arch Docker, English translation

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Infrastructure modernization across CI, dependencies, release pipeline, and documentation.

CI pipeline

• Job chain: clippy → test → [simulation, bench] — simulation and bench fan out in parallel after tests pass
• Conditional multiplatform: all 3 platforms on push to main, ubuntu-only on PRs
• Removed redundant cargo check — clippy is a superset
• Reusable composite action (.github/actions/setup-rust-env) for toolchain, flatc, system deps, Swatinem/rust-cache@v2
• [profile.dev] debug = "line-tables-only" — smaller artifacts, faster linking

os: ${{ github.event_name == 'push' && fromJson('["ubuntu-latest","macos-latest","windows-latest"]') || fromJson('["ubuntu-latest"]') }}

FlatBuffers v24 → v25.12.19

• Workspace dep and all FLATC_VERSION refs updated
• Removed mismatched_lifetime_syntaxes allow (fixed upstream)

Multi-arch Docker release

• Dockerfiles use TARGETARCH for arch-aware flatc install (prebuilt on amd64, cmake source build on arm64)
• Release workflow: QEMU + Buildx for linux/amd64,linux/arm64

Documentation: German → English

Full translation of README.md, HOWTO.md, CLAUDE.md, docker-compose.yml, .env.example, edgesync-revised.html. All TODO items marked complete.

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Pull request overview

This PR modernizes the EdgeSync v2 project infrastructure with comprehensive updates to CI/CD, dependencies, Docker deployment, and documentation translation from German to English.

Changes:

• Restructured CI pipeline with conditional multiplatform testing (all 3 OSes on push to main, ubuntu-only on PRs), reusable composite action for environment setup, and removed redundant cargo check
• Upgraded FlatBuffers from v24 to v25.12.19 across all build configurations and removed now-unnecessary mismatched_lifetime_syntaxes allow directive
• Added multi-architecture Docker support (linux/amd64, linux/arm64) with architecture-aware FlatBuffers installation
• Translated all German documentation, comments, and UI text to English across README.md, HOWTO.md, CLAUDE.md, docker-compose.yml, .env.example, and edgesync-revised.html

Reviewed changes

Copilot reviewed 13 out of 14 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
.github/workflows/ci.yml	Refactored to use composite action, added multiplatform matrix, removed cargo check
.github/workflows/release.yml	Updated to use composite action, added QEMU and multi-arch Docker builds
.github/actions/setup-rust-env/action.yml	New reusable composite action for Rust, FlatBuffers, and system dependency setup
Cargo.toml	Updated FlatBuffers to 25.12.19, added [profile.dev] with debug = "line-tables-only"
crates/edgesync-shared/src/generated/mod.rs	Removed mismatched_lifetime_syntaxes allow (fixed upstream in FlatBuffers v25)
Dockerfile.edge	Added TARGETARCH support with prebuilt binary for amd64, source build for arm64
Dockerfile.cloud	Added TARGETARCH support with prebuilt binary for amd64, source build for arm64
README.md	Complete translation from German to English, updated FlatBuffers version reference
HOWTO.md	Complete translation from German to English with all sections
CLAUDE.md	Complete translation from German to English, added release workflow reference
docker-compose.yml	Translated all comments from German to English
.env.example	Translated header comments from German to English
edgesync-revised.html	Full translation of HTML content and UI text from German to English
todo.md	Marked multiplatform and translation tasks complete, fixed "soruces" typo

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