feat(v1.1.3-modules): shared types, migrations, engine + resolver scaffold

Lays down the v1.1.3 plumbing:

- `ScriptKind` enum in `picloud-shared` ('endpoint' | 'module').
- `ModuleSource` trait + `ModuleScript` DTO + `NoopModuleSource` in
  `picloud-shared`. Resolver lives in `executor-core`; Postgres impl
  in `manager-core` (`PostgresModuleSource`).
- `Services::new` grows a fifth `modules: Arc<dyn ModuleSource>` arg.
- `ScriptValidator` returns `ValidatedScript { imports }` so the
  manager can populate the dep-graph table on save. New
  `validate_module` method on the trait gates module-shape rules.
- `Engine::execute_ast(&Arc<rhai::AST>, req)` lets the orchestrator's
  script cache reuse compiled ASTs. `Engine::execute(&str, req)` is
  preserved as a convenience that compiles inline. `Engine::compile`
  exposes the AST for callers that want to cache.
- `PicloudModuleResolver` replaces `DummyModuleResolver` per-call.
  Bridges Rhai's sync `ModuleResolver::resolve` to async
  `ModuleSource::lookup` via `Handle::block_on`. Enforces:
  - cross-app isolation (resolver captures `Arc<SdkCallCx>`),
  - circular import detection (in-progress stack on the resolver),
  - import depth limit (default 8 via
    `Limits::module_import_depth_max`).
- Module-shape validation walks `ast.statements()` via `rhai/internals`
  and accepts only `Var { CONSTANT }`, `Import`, and `Noop`. The
  manager admin endpoint runs `validate_module` at save (primary
  gate); resolver re-runs it at load (defense in depth).
- LRU cache `(AppId, name) -> (updated_at, Arc<Module>)` owned by
  `Engine`. Size from `PICLOUD_MODULE_CACHE_SIZE` (default 512).
- Migration `0015_scripts_kind.sql` adds `scripts.kind` + composite
  index + module-name shape CHECK.
- Migration `0016_script_imports.sql` adds the dep-graph table with
  FK CASCADE on both columns.
- Repo: `kind` threaded through SELECT/INSERT/UPDATE. New
  `count_routes_for_script` / `count_triggers_for_script` /
  `list_imports` methods. `create`/`update` open a transaction and
  call `replace_imports_tx` to populate the dep-graph.
- Admin endpoint: accepts `kind`; rejects reserved module names;
  rejects `endpoint → module` transitions when routes / triggers
  exist.
- SDK_VERSION 1.3 → 1.4.

Workspace builds; full test suite (~440 tests) green.

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

crates/shared/src/lib.rs

@@ -16,6 +16,7 @@ pub mod ids;
 pub mod inbox;
 pub mod kv;
 pub mod log_sink;
+pub mod modules;
 pub mod outbox_writer;
 pub mod route;
 pub mod sandbox;
@@ -40,12 +41,13 @@ pub use inbox::{
 };
 pub use kv::{KvError, KvListPage, KvService, NoopKvService};
 pub use log_sink::{ExecutionLogSink, LogSinkError};
+pub use modules::{ModuleScript, ModuleSource, ModuleSourceError, NoopModuleSource};
 pub use outbox_writer::{HttpDispatchPayload, NewHttpOutbox, OutboxWriter, OutboxWriterError};
 pub use route::{DispatchMode, HostKind, PathKind, Route};
 pub use sandbox::ScriptSandbox;
-pub use script::Script;
+pub use script::{Script, ScriptKind};
 pub use sdk_cx::SdkCallCx;
 pub use services::Services;
 pub use trigger_event::{DeadLetterEventDetail, DocsEventOp, KvEventOp, TriggerEvent};
-pub use validator::{ScriptValidator, ValidationError};
+pub use validator::{ScriptValidator, ValidatedScript, ValidationError};
 pub use version::{API_VERSION, PRODUCT_VERSION, SDK_VERSION, WIRE_VERSION};