feat: --page launch argument to open the app on a given page (e.g. --page quota)

[ahmed-khaire]

What

Adds a --page <id> launch argument so EasyCLIProxyAPI can be opened directly on a page instead of Home, e.g. EasyCLIProxyAPI --page quota for OAuth → Quota Lookup. When an instance is already running, the running window is raised and switched to that page; no second window.

Motivation: tray helpers / launchers that want to jump straight to quota details. Today there is no deep link, and driving the page through the accessibility layer crashes the WebKit view on Linux.

How

Rust (src-tauri/src/launch_navigation.rs, main.rs)

• --page <id> and --page=<id> are parsed before the instance guard.
• Single instance: value is kept in managed LaunchPageState; the frontend reads it once via the take_launch_page command.
• Second launch: if the instance lock is held, the request is written to <tmp>/EasyCLIProxyAPI-navigate-<instance key>.txt and the process exits. The running instance polls that file (500 ms), consumes it, reveals the main window (tray helper on macOS/Windows, show/unminimize/set_focus elsewhere) and emits navigate-page.
• Values are sanitised to [A-Za-z0-9/-], max 64 chars; anything unknown is ignored by the frontend.

Frontend (src/launchNavigation.ts, App.tsx, ManagementPages.tsx)

• parseLaunchTarget accepts sidebar page ids, oauth/<subpage>, and the bare OAuth subpage aliases quota / authFiles / login.
• The target is held as pending and applied only once canOpenAppPage(page, coreRunning) is true, because pages other than Home/Usage/… unlock when the core is running and the existing reset-to-home effect would otherwise win.
• OAuthManagementPage accepts a requestedSubpage and switches its tab.

Docs: README "Launch arguments" section.

Tests

• tests/launchNavigation.test.ts (parser) and src-tauri/src/tests/launch_navigation.rs (argument parsing, sanitising, request file round-trip): all pass.
• bun run check clean. bun test: 148 pass, 1 pre-existing failure (i18n > keeps both locale dictionaries structurally aligned) that also fails on main.
• cargo test: 329 pass; agent_probe_command_stops_at_timeout fails on my Ubuntu 24.04 host on main as well (timing), unrelated.
• Manual on Linux (debug build with embedded frontend): --page usage-records on first launch → Usage; --page home from a second launch → forwarded, one window, request file consumed; --page quota → held while the core was starting, then OAuth / Quota Lookup selected.

Not tested on macOS/Windows; the reveal path there reuses the existing tray::show_main_window.