v1.7.2 — fresh-install one-liner hotfix

v1.7.1 shipped the curl-installer one-liner but `memphis init` failed on a fresh PC because install.sh skipped `npm run bootstrap`. The README's manual flow hit the same wall. Effectively no documented fresh-install path produced a working install. v1.7.2 closes that gap.

The fix (#316)

1. `install.sh` runs `npm run bootstrap` unconditionally between `npm link` and the optional `memphis init`. Bootstrap creates `.env` from `.env.example`, generates random API token + vault pepper, ensures the agent profile, optionally installs the user systemd unit. Without this every install ended in "linked CLI that can't run init".

2. `memphis init` auto-creates `.env` from `.env.example` as a safety net — operators who skip install.sh's bootstrap step (manual clone + build, or install.sh without `--with-init`) now get a working init with a warning recommending `npm run bootstrap` for token generation, instead of a hard error.

3. `bootstrap.sh vault_initialized()` checks the right path — was `${HOME}/.memphis/vault/vault-entries.json` (with `/vault/` subdir that doesn't exist), now `${HOME}/.memphis/vault-entries.json`.

Verified

End-to-end on a fresh clone in /tmp:

```
git clone --depth 1 https://github.com/Memphis-Chains/memphis.git memphis
cd memphis && npm install && npm run build
node dist/infra/cli/index.js init --non-interactive --passphrase X --recovery-question Q --recovery-answer A --json
```

Result: vault initialized, operator configured, 2 chain blocks created, single command.

The one-liner now works

```bash
curl -fsSL https://raw.githubusercontent.com/Memphis-Chains/memphis/main/scripts/install.sh | bash -s -- --with-init
```

Goes from clean PC to running operator with vault, identity, and first chain writes — end of session.

Existing v1.7.1 installs

If you already pulled v1.7.1 and got the broken `memphis init` error, run once:

```bash
cd ~/memphis
git pull && npm run build
npm run bootstrap # creates .env + tokens, installs systemd unit
memphis init # vault passphrase, recovery Q/A, operator passphrase
memphis provider add # hidden TTY prompt for API key
```

🤖 Generated with Claude Code

What's Changed

• fix(install): unblock fresh-install one-liner — bootstrap before init + auto-create .env by @Memphis-Chains in #316
• release(v1.7.2): version bump + changelog for fresh-install hotfix by @Memphis-Chains in #317

Full Changelog: v1.7.1...v1.7.2