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/main.rs

@@ -12,6 +12,7 @@ use clap::{Args, Parser, Subcommand, ValueEnum};
 mod client;
 mod cmds;
 mod config;
+mod linkstate;
 mod manifest;
 mod output;
 
@@ -191,6 +192,10 @@ struct ApplyArgs {
     /// non-interactively (CI).
     #[arg(long)]
     yes: bool,
+    /// Skip the bound-plan staleness check (apply even if the app changed
+    /// since the last `pic plan`).
+    #[arg(long)]
+    force: bool,
 }
 
 #[derive(Args)]
@@ -1112,7 +1117,9 @@ async fn main() -> ExitCode {
         }
         Cmd::Logout => cmds::logout::run().await,
         Cmd::Whoami => cmds::whoami::run(mode).await,
-        Cmd::Apply(args) => cmds::apply::run(&args.file, args.prune, args.yes, mode).await,
+        Cmd::Apply(args) => {
+            cmds::apply::run(&args.file, args.prune, args.yes, args.force, mode).await
+        }
         Cmd::Plan(args) => cmds::plan::run(&args.file, mode).await,
         Cmd::Pull(args) => cmds::pull::run(&args.app, &args.dir, mode).await,
         Cmd::Init(args) => cmds::init::run(