feat(cli): add pic command-line client (login, apps, scripts, logs)

Adds a new workspace crate `picloud-cli` shipping a `pic` binary that
drives the edit-deploy-invoke-tail-logs loop against PiCloud's admin
and execute HTTP surface. Eight subcommands cover the minimum a
developer needs to never open the dashboard:

  pic login                    (paste URL + bearer token, validates via /auth/me)
  pic whoami                   (re-validates and prints principal)
  pic apps ls | create
  pic scripts ls | deploy | invoke
  pic logs <id>

Credentials persist as TOML under the platform config dir (resolved
via `directories`); on POSIX the file is forced to mode 0600.
PICLOUD_URL + PICLOUD_TOKEN env vars short-circuit interactive prompts
for CI and integration tests.

The CLI redeclares minimal request/response structs in `client.rs`
rather than depending on `manager-core` — keeps the blast radius
contained without touching the existing crate boundaries.

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

crates/picloud-cli/src/cmds/mod.rs

@@ -0,0 +1,5 @@
+pub mod apps;
+pub mod login;
+pub mod logs;
+pub mod scripts;
+pub mod whoami;