feat(modules): install, uninstall, purge and restart (phase 4, slice 1)

The consumer half of a release module-uo's CI has been publishing since
phase 3 closed. Before this, core had the installed_modules provenance
columns and no code that could ever fill them: nothing fetched, verified,
unpacked, removed or purged anything, and there was no admin route at all.

Adds modules/archive.js, modules/install.js, schema.runPurge(),
lifecycle.stop(), loader.stopHook(), and /api/v1/admin/modules with eight
routes. 797 server tests (+76), manifest 158 -> 166 + 2 internal, OpenAPI
gains 8 operations and loses nothing.

Reject, never sanitise
----------------------
The download is the easy part: an https-only allowlist re-checked on every
redirect hop, a declared sha256 compared against the bytes that arrived, and
a byte cap. Unpacking is where the archive chooses the filenames, and core
writes into a directory bind-mounted from the host, so an escape is not
confined to the container.

archive.js inspects the whole archive before a byte is unpacked and refuses
absolute and drive-absolute paths, `..` segments, NUL bytes, backslashes,
anything that is not a regular file or a directory, more than one top-level
entry, and anything over the entry or byte caps. Refusing symlinks and
hardlinks outright is what keeps this off the majority of node-tar's
published advisories rather than depending on the library to contain them.

That two-pass shape is load-bearing, and it was measured rather than assumed:
extracting an archive whose fourth member escapes upward throws under
node-tar 7.5.22 -- and leaves the first three members on disk. The loader
scans that directory at require time on the next boot, so a half-unpacked
module is a module. Everything therefore happens in a scratch directory that
is removed on any failure, and the move into place is the last step.

`tar` is pinned to ^7.5.22 rather than the ^6 that installs by default: 6.x
is flagged critical, and reading the advisory list is what the file's header
now says out loud -- almost all of it is hardlink or symlink traversal and
PAX header interpretation differentials, which is exactly this feature's
threat model.

Two things the plan had wrong
-----------------------------
The bundle's top-level directory is `module-uo-<version>`, not the module id
-- so "the top-level name must equal the id" was checked against nothing real.
The extractor strips that level instead, because its name belongs to whoever
published the bundle and the directory it lands in is core's. What is checked
instead is the unpacked module.json: a manifest promising `uo` and delivering
something else is refused rather than installed under the name it promised.

And purge cannot be a follow-up action (decision 5): purge.sql lives inside
the directory uninstall deletes. It is offered in the uninstall flow and as a
standalone action on a still-installed module, and the standalone one refuses
unless the module is already disabled -- dropping tables under something that
is still serving leaves it answering out of a world that no longer exists.

Disable now means stopped
-------------------------
lifecycle.stop() dispatches that one module's onShutdown before flipping the
guard, so a module an operator switches off actually releases its sockets and
closes its streams instead of merely becoming unreachable. The hook runs
first and the state moves after it, because while onShutdown runs the module
is still `started` and that is the only state in which its routes and the
world it is tearing down agree. A hook that throws does not stop the disable
-- the opposite of the boot path's rule, and deliberately.

Enable is not its mirror and there is no start(id) beside it. There is no
onBoot re-dispatch and the hooks were never promised re-entrant, so enable
moves the row and the restart route starts it. A test pins that enable does
not touch the loader, because "fixing" it is a one-line change that would put
a module with closed sockets back on the nav.

Restart raises SIGTERM against its own process rather than calling the
shutdown path directly, so server.js's handler stays the one graceful-shutdown
path and this route cannot drift from it.

The allowlist bootstraps from MODULE_SOURCE_HOSTS into a settings row and is
admin-managed after that (decision 6); seedDefault is INSERT IGNORE, so
changing the variable on an existing deployment is a no-op by design. An empty
list forbids every install rather than allowing every host -- the safe
direction for a value someone might blank by accident.

Verified against the real v0.3.0 release
----------------------------------------
Not a fixture: fetched the published install manifest over the real Gitea
host and its redirect chain, verified the sha256, inspected and unpacked the
252,517-byte artifact to 82 files, and then booted core against the result --
the module registered its five mounts, seven streams and eight capabilities
and resolved its client chunk, with no scratch directory left behind.

Two defects this slice's own tooling caught, both of which had already been
written down as classes:
  - the controller destructured runPurge at require time, capturing the
    function rather than the module, which made the one dependency whose
    ORDER matters the one that could not be substituted;
  - two swagger annotations carried an apostrophe inside a quoted string,
    dropped silently by swagger-autogen before slice 5 taught it to fail loudly.

Co-Authored-By: Claude <noreply@anthropic.com>

server/src/modules/lifecycle.js

@@ -205,4 +205,67 @@ async function shutdown({ modules, budgetMs = SHUTDOWN_BUDGET_MS } = {}) {
   }
 }
 
-module.exports = { boot, shutdown, SHUTDOWN_BUDGET_MS }
+/**
+ * Stop ONE module and mark it disabled — the admin panel's Disable (§2.7.2
+ * decision 3).
+ *
+ * Phase 2 built disable as a pure state flip: the record moved to `disabled` and
+ * the dispatch guard started answering 404. That makes a module invisible, not
+ * stopped. Everything a module does that is not a response to a request — the
+ * sockets and timers its `onBoot` armed — carried on running, so an operator
+ * disabling a module *because* it was misbehaving got nothing until the next
+ * restart, which is the one thing the button was supposed to save them.
+ *
+ * So the hook runs first, and the state moves after it: while `onShutdown` is
+ * running the module is still `started`, which is the only state in which its
+ * own routes and the things it is tearing down are consistent with each other.
+ * The hook gets the same budget the exit path gives it.
+ *
+ * A hook that throws does NOT stop the disable. The operator asked for this
+ * module to stop answering; a module that could not close cleanly is a reason to
+ * log loudly, not a reason to leave it serving. That is the opposite of the boot
+ * path's rule, and deliberately: there, a failure means the module never became
+ * safe to use.
+ *
+ * **Enable is not the mirror of this, and there is no `start(id)` beside it.**
+ * There is no `onBoot` re-dispatch, and MODULE_API.md has never promised the
+ * hooks are re-entrant — no module author has written `onBoot` to be safe to run
+ * twice in one process. Re-enabling therefore moves the row and waits for a
+ * restart, which the admin screen offers.
+ *
+ * @returns {Promise<{stopped: boolean, error: string|null}>} whether a hook ran.
+ */
+async function stop(id, { modules, model, budgetMs = SHUTDOWN_BUDGET_MS } = {}) {
+  /* eslint-disable global-require */
+  const loader = modules || require('./loader')
+  const rows = model || require('../model/modules/modules.model')
+  /* eslint-enable global-require */
+
+  let error = null
+  let stopped = false
+
+  if (loader.isLoaded()) {
+    const target = loader.stopHook(id)
+    if (target) {
+      try {
+        await withBudget(target.hook, budgetMs)
+        stopped = true
+        log.info(`module "${id}" stopped by an operator`)
+      } catch (err) {
+        error = err.message
+        log.warn(`module "${id}" onShutdown failed or timed out while being disabled — disabling anyway`, {
+          error: err.message,
+        })
+      }
+    }
+    // Unconditional, and after the hook: this is what makes its routes and its
+    // client chunk answer 404 (§4.5). A module that is not loaded in this
+    // process has no record to move, and setState ignores an unknown id.
+    loader.setState(id, 'disabled')
+  }
+
+  await safe(`disabling module "${id}"`, () => rows.disable(id))
+  return { stopped, error }
+}
+
+module.exports = { boot, shutdown, stop, SHUTDOWN_BUDGET_MS }