fix(import): bound what an export may inflate to, allow one import per account, and never leave the upload behind

The extractor held the inflated export.xml to a flat 8 GiB whatever the
member occupied, and the header ratio check reads sizes the archive
writes itself: a member declaring an honest ratio could inflate at
1000:1, so an 8 MB upload could fill the temp directory. The streamed
byte count is now held to 200 times the member's compressed size on
disk (never less than 64 MiB, never more than 8 GiB), and a stored
member may not grow at all.

An account may have one Apple Health import queued or running. A
second upload with different bytes is refused with 409
import.apple_health.busy and the running job's id; the check and the
new row are one transaction under an advisory lock.

The staged upload is the person's export in plain text. It is now
removed on every exit that leaves no worker to read it: a refused or
broken multipart body, no worker running, a queue that takes no job
(the row is failed as well), the admin route's missing or unknown
target account, and an account deleted before the worker reached it.
The worker removes the files before recording a failure, so a row that
went with a deleted account no longer strands them. The 15-minute
import reconcile pass also sweeps staged files older than the longest
an import may run.

src/lib/openapi/error-codes.ts

@@ -168,7 +168,7 @@ export const ERROR_CODE_CATALOGUE: Readonly<Record<string, readonly string[]>> =
       "illness.episode.parent-not-found",
       "illness.insights.invalid",
     ],
-    import: ["import.write_failed"],
+    import: ["import.apple_health.busy", "import.write_failed"],
     ingest: ["ingest.rate_limited"],
     insights: [
       "insights.generate.budgetExceeded",

src/lib/openapi/routes/import.ts

@@ -324,6 +324,11 @@ export const importPaths: NonNullable<ZodOpenApiObject["paths"]> = {
           content: { "application/json": { schema: errorEnvelope } },
         },
         ...stdResponses,
+        "409": {
+          description:
+            "An import for this account is already queued or running, and these bytes are not the ones it carries (the same bytes resolve to that job as a 202). `meta.errorCode` is `import.apple_health.busy` and `meta.jobId` names the running job; poll it, then upload again. The upload was discarded.",
+          content: { "application/json": { schema: errorEnvelope } },
+        },
         "422": {
           description:
             "The multipart body could not be streamed to disk — no `file` part, a malformed boundary, or the size cap tripped mid-stream. The message names the failure.",
@@ -335,7 +340,7 @@ export const importPaths: NonNullable<ZodOpenApiObject["paths"]> = {
         },
         "503": {
           description:
-            "No background worker is bound to this process, so the job cannot be queued. The upload was staged and is discarded; retry once a worker is running.",
+            "No background worker is bound to this process, or the queue did not accept the job, so nothing will run it. The staged upload is discarded (and a created job is marked failed); retry once a worker is running.",
           content: { "application/json": { schema: errorEnvelope } },
         },
       },