fix(docsync): an idle WebDAV binding read as an emptied folder, and two ids nobody checked

The audit's worst find, reproduced against a live Nextcloud before and after the
fix: the WebDAV adapters answer "nothing changed here" by returning an EMPTY
listing plus `cursorUnchanged`, and nothing read that flag — `grep -rn
cursorUnchanged src/` found it set by four adapters and consulted by none. The
core therefore saw a folder that had lost everything. Run 1 and 2 look fine
because the run's own uploads move the ETag; from run 3 on, every run of an
idle binding ends `partial` with `mass_delete_guard` and six documents reported
missing, forever, until failure_count opens the circuit and the scheduler drops
the binding entirely. That is the ordinary case — a binding nobody is touching.
planReconcile now takes `remoteUnchanged` and plans only what happened in TREK.

Two ids were authorised by trip and never checked against it:

  - resolveConflict took an item id on trust, so the owner of any trip could
    decide a conflict belonging to somebody else's. Both are plain integers and
    nothing compared them.
  - The connection test merged the STORED credential into a probe of whatever
    baseUrl the caller named — a way to have TREK post another account's API
    token at a server of the caller's choosing. Stored secrets are now reused
    only for the address they were stored against.

The phone's connect form was wrong in three ways at once, each of which the
desktop had right: it read the address as `baseUrl` while the field is
`base_url` (so every connection it saved carried an empty address), it drew
`allow_insecure_tls` as a text box and always sent false, and it built label
keys as `docsync.provider${cap(label)}` when the label column already holds the
full suffix — `docsync.providerProviderApiKey`, rendered raw on screen. Those
rules are not markup, so they now live in `useConnectForm`, which both shells
use. Its test fixture invented the field shape and so agreed with the broken
sheet; it now mirrors document_provider_fields.

Also: the scheduler read its interval once at bootstrap while this file's own
comment promised a per-tick read, so changing it did nothing until a restart;
and dueLinks ordered by a column that a successful run clears, which left every
binding tied and SQLite answering in insertion order — on a database with 170
bindings the same twenty ran on every tick and nothing created after them was
ever synced automatically.

server/src/nest/doc-sync/doc-sync.controller.ts

@@ -150,7 +150,13 @@ export class DocSyncController {
     const existing = this.config
       .listConnections(Number(tripId))
       .find((c) => c.provider_id === body.providerId);
-    const stored = existing ? this.config.toRef(existing) : null;
+    // Only for the address the credential was stored against. Merging it into a
+    // probe of an arbitrary baseUrl turns this route into a way to have TREK
+    // post a stored API token at a server of the caller's choosing — which is
+    // exactly what somebody who inherited a trip but not its credentials would
+    // reach for. Same host, same scheme, same port, or the caller types it in.
+    const sameTarget = !!existing && sameOrigin(existing.base_url, urlCheck.data.url);
+    const stored = sameTarget && existing ? this.config.toRef(existing) : null;
     const fields = this.config.providerFields(body.providerId);
     const secrets: Record<string, string> = { ...(stored?.secrets ?? {}) };
     const settings: Record<string, string> = { ...(stored?.settings ?? {}) };
@@ -356,12 +362,25 @@ export class DocSyncController {
     @Body() body: DocsyncResolveConflictDto,
   ) {
     this.assertOwner(tripId, user);
-    const ok = await this.sync.resolveConflict(Number(itemId), body.keep);
+    const ok = await this.sync.resolveConflict(Number(itemId), body.keep, Number(tripId));
     if (!ok) throw new HttpException('Item is not in conflict', 400);
     return { success: true };
   }
 }
 
+
+/** Whether two URLs address the same server, for deciding if a stored secret may be reused. */
+function sameOrigin(a: string | null | undefined, b: string): boolean {
+  if (!a) return false;
+  try {
+    const x = new URL(a);
+    const y = new URL(b);
+    return x.protocol === y.protocol && x.host === y.host;
+  } catch {
+    return false;
+  }
+}
+
 /**
  * The origin a provider has to call back on.
  *