feat(vars): admin CRUD API + pic vars CLI

Completes the vars half of Phase 3 end-to-end:
- vars_repo: VarOwner{Group|App} upsert/delete/list (owner-kind-specific
  SQL; ON CONFLICT restates the partial-index predicate).
- vars_api: GET/PUT/DELETE under /apps/{id}/vars and /groups/{id}/vars,
  resolve-then-require gated on App/GroupVars{Read,Write}, secrets-style
  error mapping + key/env-scope validation.
- pic vars ls/set/rm (--group|--app, --env, --json, --tombstone).
- journey test: a group var is inherited by a descendant app's
  vars::get(), and an app-level value overrides it (proximity) — green.

386 manager-core lib tests + the vars journey pass; clippy clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/picloud-cli/tests/cli.rs

@@ -37,3 +37,4 @@ mod scripts;
 mod secrets;
 mod staleness;
 mod triggers;
+mod vars;

crates/picloud-cli/tests/fixtures/read-var.rhai

@@ -0,0 +1,4 @@
+// Phase-3 vars journey fixture: returns the resolved `region` config var
+// verbatim so the test can assert on inheritance (group value) vs an app
+// proximity override.
+vars::get("region")

crates/picloud-cli/tests/vars.rs

@@ -0,0 +1,84 @@
+//! Phase-3 config `vars`, end to end via `pic`: a group-owned var is
+//! inherited by an app underneath it, and an app-owned var of the same key
+//! overrides the inherited value (proximity wins, §3).
+//!
+//! Drives the real resolution path: a script does `vars::get("region")`
+//! and returns it; we invoke it via `/api/v1/execute/{id}` and assert on
+//! the body. First the group value flows down (inheritance), then an app
+//! value shadows it (override).
+
+use crate::common;
+use crate::common::cleanup::{AppGuard, GroupGuard};
+
+#[ignore = "needs DATABASE_URL pointing at a running Postgres"]
+#[test]
+fn group_var_is_inherited_then_app_value_overrides() {
+    let Some(fx) = common::fixture_or_skip() else {
+        return;
+    };
+    let env = common::admin_env(fx);
+    let acme = common::unique_slug("v-acme");
+    let app = common::unique_slug("v-app");
+
+    // Group `acme`, then a `region` var on it (a JSON string "eu").
+    let _g_acme = GroupGuard::new(&env.url, &env.token, &acme);
+    common::pic_as(&env)
+        .args(["groups", "create", &acme])
+        .assert()
+        .success();
+    common::pic_as(&env)
+        .args(["vars", "set", "region", "eu", "--group", &acme])
+        .assert()
+        .success();
+
+    // App under acme with a script that reads + returns the resolved var.
+    let _app = AppGuard::new(&env.url, &env.token, &app);
+    common::pic_as(&env)
+        .args(["apps", "create", &app, "--group", &acme])
+        .assert()
+        .success();
+    let fixture = common::fixture_path("read-var.rhai");
+    common::pic_as(&env)
+        .args([
+            "scripts",
+            "deploy",
+            fixture.to_str().unwrap(),
+            "--app",
+            &app,
+        ])
+        .assert()
+        .success();
+
+    // Resolve the deployed script's id.
+    let ls = common::pic_as(&env)
+        .args(["scripts", "ls", "--app", &app])
+        .output()
+        .expect("scripts ls");
+    let id = common::parse_first_id(std::str::from_utf8(&ls.stdout).unwrap())
+        .expect("scripts ls should produce one row");
+
+    // Inherited: the app has no own `region`, so the group's "eu" resolves.
+    assert_eq!(invoke_body(&env, &id), serde_json::json!("eu"), "inherited");
+
+    // Proximity override: an app-owned `region` shadows the group value.
+    common::pic_as(&env)
+        .args(["vars", "set", "region", "us", "--app", &app])
+        .assert()
+        .success();
+    assert_eq!(invoke_body(&env, &id), serde_json::json!("us"), "override");
+}
+
+/// Invoke a script via `pic scripts invoke <id>` (→ `/api/v1/execute/{id}`)
+/// and parse its JSON body.
+fn invoke_body(env: &common::TestEnv, id: &str) -> serde_json::Value {
+    let out = common::pic_as(env)
+        .args(["scripts", "invoke", id])
+        .output()
+        .expect("scripts invoke");
+    assert!(
+        out.status.success(),
+        "invoke failed: {}",
+        String::from_utf8_lossy(&out.stderr)
+    );
+    serde_json::from_slice(&out.stdout).expect("invoke body is JSON")
+}