docs: explain cleanup after platform database loss (#593)

## Summary

Document the local recovery files to remove only when the installation
database is permanently lost and the installation will not be recovered.
Clarify that removing those files does not delete Cloudflare resources
and link to the existing manual cleanup sequence.

Fixes #428

## Verification

- Before: the uninstall guide provided no local cleanup path when the
installation database was unavailable.
- After: `npm exec --yes --package=pnpm@12.11.2 -- pnpm --filter
@void/docs build` completed successfully; `git diff --check` passed.
- Not verified: recovery or deletion against a live Cloudflare
installation.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Signed-off-by: jay23606 <4602056+jay23606@users.noreply.github.com>
Co-authored-by: Claude Haiku 5.5 <noreply@anthropic.com>

Author: jay23606

docs/guide/platform/installation/uninstall.md

@@ -91,6 +91,8 @@ If installation configured Cloudflare Access, the uninstall plan lists its recor
 
 Uninstall does not remove the applications created for [project Zero Trust](/guide/platform/administration/zero-trust). While Zero Trust is enabled or still has Access applications, uninstall and `--plan` stop before any change and list those applications. Run `void platform zero-trust disable` first. Uninstall reads this from the installation database, so it also stops when the database cannot be reached.
 
+If the installation database is permanently gone and cannot be restored, there is no uninstall command that can clear the local installation record or list its Cloudflare resources. Once you have decided not to recover that installation, delete `~/.void/platforms/<account-id>/<installation-id>.json` and any sibling `<installation-id>.recovery.enc` or `<installation-id>.secrets.enc` files. This removes only local state and encrypted credentials; it does not delete Cloudflare resources. Review and remove those resources manually using [Remove retained resources](#remove-retained-resources).
+
 If no platform user exists yet, for example because first administrator setup did
 not finish, nobody can run `zero-trust disable`. Uninstall then turns off project
 Zero Trust and deletes its applications itself. Run it on the computer that installed