feat: Rust port of kopdeltav — eliminate Python dependency for desktop app - #12

Port the Python kopdeltav/parser.py to Rust with 1:1 logic parity.
Two-layer design: low-level ConfigNode tree parser and high-level
CelestialBody extractor. Handles comments, MM modifiers, delete
directives, curve keys with tangent defaults, inline brace formats,
unclosed brace recovery, and #LOC_ display name fallback.

Port all calculator functions from Python kopdeltav/calculator.py to Rust:
- Orbital mechanics: low_orbit_altitude, circular/escape velocity
- Atmospheric density via hermite-interpolated curves (kPa->Pa conversion)
- Launch delta-V with empirical gravity/drag/jet estimation
- Hohmann transfer (inward + outward) via vis-viva equation
- Tsiolkovsky rocket equation for mass ratio
- Geostationary orbit altitude and transfer delta-V
- Escape/landing delta-V helpers
- Multi-step route planner (compute_route)

All 17 tests pass including reference value regression tests:
- Sanctar escape velocity: 3802 m/s
- Kerbin escape velocity: 3431 m/s
- Sanctar surface density: 1.4096 kg/m3
- Sanctar launch rocket: ~3110 m/s, with jets: ~1982 m/s

Add system.rs with build_tree, is_barycenter, sort_by_transfer_dv,
and scan_configs. Add i18n.rs with full ja/en/id translation tables
and get_text/get_all_keys API with language fallback.

Replace the Python subprocess spawning architecture with native Rust
Tauri commands that directly call the kopdeltav crate. Add state.rs
for shared AppState (bodies + system tree) and commands.rs with 13
IPC handlers covering health, config upload, GameData scan, body
listing/detail, launch/hohmann/tsiolkovsky calculations, system
tree, destinations, route planning, atmosphere profiles, and moon
queries. Remove tauri-plugin-shell dependency and Python resource
bundling from tauri.conf.json.

Migrate all HTTP fetch-based API calls in useApi.ts to Tauri invoke()
from @tauri-apps/api/core, update ConfigUpload.vue to read file as text
before passing to invoke, and remove the vite dev server proxy config.

…uri commands

…esolution