Condenser: Node backend port (replace the Python backend)

[mdeguzis]

Condenser backends are Node only and ship as a single backend.mjs, so main.py + lib/*.py cannot ship. Reimplement the backend surface in Node, or delegate to the web API where possible.

Local-only work that must be Node: system info (os + exec), Steam library scan (fs), proton-ge and compat tool install (fs/exec/tar), launch option writes, cdn cache, logging. Network work (ProtonDB, Supabase) can be plain fetch in Node with no CORS limit, or delegate to the existing edge functions. Document what stays local vs delegated.

[mdeguzis]

Node backend skeleton is in and runtime-verified (it is plain Node, so it runs outside Steam). Split into condenser/backend/ modules.

Ported and tested: get_system_info + get_protondb_systeminfo (os/exec/fs, returns the SystemInfo shape), copy_to_clipboard (wl-copy/xclip/pbcopy/clip), get_plugin_version + get_build_commit (baked at build via esbuild define so they survive install), get_log_contents/set_log_level/log_frontend_event (file logger under ~/.condenser/logs), fetchProxy + getProtonDbSummary (Node fetch, no CORS). A quick node import of backend.mjs returned live hardware, the right version/commit, and a real ProtonDB summary.

Stubbed with structured { ok:false, notImplemented, action, reason } and grouped by why:

• self-updater + restart_plugin_loader: Condenser owns plugin updates via its registry
• proton-ge / compat tools / lsfg installers: OS-specific, not ported yet
• get_game_source/platforms/grid_artwork/shortcut_name: needs the Steam library scan wired
• cef debugging toggle: Condenser already runs with CDP enabled

Next: pick off the library-scan group (drives several tabs) and decide delegate-to-web vs local for game_requirements.