feat(project-tool): bound-plan staleness check (content fingerprint)

`pic plan` now records a fingerprint of the live state it diffed against;
`pic apply` replays it and the server refuses (HTTP 409) if the app
changed underneath the reviewed plan — the §4.2 "apply exactly what you
reviewed" guarantee, in its content-addressed form (no migration, no
changes to interactive write paths).

Server (manager-core):
- `state_token(CurrentState)`: deterministic FNV-1a fingerprint over what
  the diff keys on — script name+version (version bumps on any edit),
  route identity+binding/attrs, trigger membership+enabled, secret names.
  Order-independent; a collision can only yield a false "unchanged", never
  a false refusal.
- `plan` returns it (flattened onto the plan JSON, so the wire stays
  additive); `apply` takes an optional `expected_token` and, under the
  apply lock before any write, returns `StateMoved` (409) on mismatch.

CLI:
- `.picloud/` link state (`linkstate`): `pic plan` writes the token scoped
  to the app slug; `pic apply` replays it, then clears it on success (the
  token is single-use — the next apply re-plans). `--force` skips the
  check; apply with no recorded plan still works standalone (today's
  behavior). `.picloud/` is already gitignored by `pic init`.

The tree-structure version (the other half of §4.2's counter) stays a
deliberate no-op until groups exist — it only guards reparent/structural
moves, which don't exist single-app.

Tested: state_token unit test (stable/order-independent/sensitive) + a
staleness journey (plan → out-of-band deploy → apply refuses → --force
applies); manager-core lib 363 + cli bins 31 + 13 journeys green; clippy
-D warnings clean.

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

crates/picloud-cli/src/client.rs

@@ -920,9 +920,14 @@ impl Client {
         app: &str,
         bundle: &serde_json::Value,
         prune: bool,
+        expected_token: Option<&str>,
     ) -> Result<ApplyReportDto> {
         let app = seg(app);
-        let body = serde_json::json!({ "bundle": bundle, "prune": prune });
+        let body = serde_json::json!({
+            "bundle": bundle,
+            "prune": prune,
+            "expected_token": expected_token,
+        });
         let resp = self
             .request(Method::POST, &format!("/api/v1/admin/apps/{app}/apply"))
             .json(&body)
@@ -965,6 +970,10 @@ pub struct PlanDto {
     pub triggers: Vec<ChangeDto>,
     #[serde(default)]
     pub secrets: Vec<ChangeDto>,
+    /// Fingerprint of the live state this plan was computed against; carried
+    /// in `.picloud/` and replayed to `apply` for the bound-plan check.
+    #[serde(default)]
+    pub state_token: String,
 }
 
 #[derive(Debug, Deserialize)]