chore: bump version to 0.7.0 + download page updates

Bumps:
- crates/{core,cli,tauri-app}/Cargo.toml: 0.6.2 → 0.7.0
- crates/tauri-app/tauri.conf.json: 0.6.2 → 0.7.0
- gen/android/app/tauri.properties: versionName 0.7.0, versionCode 7000

website/download.html: v0.7.0 promoted to top with FoF release notes;
v0.6.2 retained in archive section. Wire-additive notice + link to
design.html#fof for full architecture.

No -beta suffix this cycle: no users on prior version means no need
for the beta carve-out. Will resume beta convention when there are
real users to migrate.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/tauri-app/tauri.conf.json

@@ -1,6 +1,6 @@
 {
   "productName": "itsgoin",
-  "version": "0.6.2",
+  "version": "0.7.0",
   "identifier": "com.itsgoin.app",
   "build": {
     "frontendDist": "../../frontend",