fix(auth): answer 503 when the session store cannot be read

The cookie resolvers folded a failed query into null, so a database restart
answered 401 and every client discarded a good credential. The lookup now
raises SessionStoreUnavailableError, which reaches the wire as 503 with
auth.session.unavailable. Logout still clears the cookie on a failed lookup
and records a warning.

docs/api/openapi.yaml

@@ -81,7 +81,9 @@ paths:
             route, including any Bearer token against an admin surface) and `auth.admin.required` (a cookie session that
             is not an admin's). A route that checks a credential of its own — sign-in, the MFA challenge exchange, a
             password confirmation — may still answer 401 with prose and no code, so a missing `meta.errorCode` means the
-            route refused the credential it was handed, not that the response is malformed."
+            route refused the credential it was handed, not that the response is malformed. A session that could not be
+            checked because the session store was unreachable is NOT a 401: it answers 503 with
+            `auth.session.unavailable`, and the client keeps its credential and retries."
           content:
             application/json:
               schema:
@@ -36112,35 +36114,35 @@ components:
                 anamnesis.lifeConfirm.invalid, anamnesis.lifeSections.invalid; auth — auth.admin.required,
                 auth.already_authenticated, auth.mfa.code_invalid, auth.missing, auth.refresh.invalid,
                 auth.refresh.reuse, auth.refresh.revoked, auth.reproof.failed, auth.reproof.required,
-                auth.reproof.too_weak, auth.scope.insufficient, auth.session.insecure_transport, auth.stepup.required,
-                auth.token.expired, auth.token.invalid; backup — backup.foreign_reference, backup.key.missing,
-                backup.payload.undecryptable, backup.restore.active, backup.section.missing, backup.upload.too_large;
-                biomarkers — biomarkers.unit.locked; body-site — body-site.invalid; coach — coach.budget.exceeded,
-                coach.conversation.invalidTitle, coach.conversation.notFound, coach.fenced.attachmentConflict,
-                coach.fenced.attachmentLimit, coach.fenced.attachmentNotFound, coach.fenced.attachmentNotIndexed,
-                coach.fenced.attachmentRequired, coach.fenced.attachmentUnavailable, coach.fenced.invalid,
-                coach.request.invalid; coach-prefs — coach-prefs.body.invalid_json, coach-prefs.body.invalid_shape;
-                consent — consent.ai.confirmRequired, consent.ai.required; cycle — cycle.bulk.invalid,
-                cycle.bulk.too_large, cycle.calendar.invalid, cycle.calendar.range, cycle.cycles.invalid,
-                cycle.day-log.conflict, cycle.day-log.invalid, cycle.disabled, cycle.period.invalid,
-                cycle.symptom.custom.invalid, cycle.symptom.custom.limit; cycle-prefs — cycle-prefs.body.invalid_json,
-                cycle-prefs.invalid; disable-coach — disable-coach.body.invalid_json; dawarich —
-                dawarich.credentials_rejected, dawarich.home_place_unknown, dawarich.invalid, dawarich.not_connected,
-                dawarich.rate_limited, dawarich.unreachable; day — day.invalid; demo — demo.readOnly; documents —
-                documents.chat.conversationNotFound, documents.chat.invalid, documents.inbound.alreadyConfirmed,
-                documents.inbound.alreadyPartlyConfirmed, documents.inbound.budgetExceeded,
-                documents.inbound.decryptFailed, documents.inbound.encounterNotFound, documents.inbound.episodeNotFound,
-                documents.inbound.extractFailed, documents.inbound.factNotFound, documents.inbound.factNotPending,
-                documents.inbound.factTypeMismatch, documents.inbound.fileTooLarge, documents.inbound.fileType,
-                documents.inbound.invalidMetadata, documents.inbound.invalidQuery, documents.inbound.invalidUpdate,
-                documents.inbound.localOcrDisabled, documents.inbound.notFound, documents.inbound.notIndexed,
-                documents.inbound.pdfNeedsAnthropic, documents.inbound.providerUnsupported,
-                documents.inbound.quotaExceeded, documents.inbound.rateLimited, documents.inbound.restoreDuplicate,
-                documents.inbound.restoreGone, documents.inbound.sourceAliasLimit, documents.inbound.uploadBusy,
-                documents.inbound.uploadTimeout, documents.inbound.vaccinationNotFound, documents.sources.authRefused,
-                documents.sources.badResponse, documents.sources.browserOnly, documents.sources.invalidAddress,
-                documents.sources.linkTargetNotFound, documents.sources.notConnected, documents.sources.notFound,
-                documents.sources.organizationRequired, documents.sources.originNotAllowed,
+                auth.reproof.too_weak, auth.scope.insufficient, auth.session.insecure_transport,
+                auth.session.unavailable, auth.stepup.required, auth.token.expired, auth.token.invalid; backup —
+                backup.foreign_reference, backup.key.missing, backup.payload.undecryptable, backup.restore.active,
+                backup.section.missing, backup.upload.too_large; biomarkers — biomarkers.unit.locked; body-site —
+                body-site.invalid; coach — coach.budget.exceeded, coach.conversation.invalidTitle,
+                coach.conversation.notFound, coach.fenced.attachmentConflict, coach.fenced.attachmentLimit,
+                coach.fenced.attachmentNotFound, coach.fenced.attachmentNotIndexed, coach.fenced.attachmentRequired,
+                coach.fenced.attachmentUnavailable, coach.fenced.invalid, coach.request.invalid; coach-prefs —
+                coach-prefs.body.invalid_json, coach-prefs.body.invalid_shape; consent — consent.ai.confirmRequired,
+                consent.ai.required; cycle — cycle.bulk.invalid, cycle.bulk.too_large, cycle.calendar.invalid,
+                cycle.calendar.range, cycle.cycles.invalid, cycle.day-log.conflict, cycle.day-log.invalid,
+                cycle.disabled, cycle.period.invalid, cycle.symptom.custom.invalid, cycle.symptom.custom.limit;
+                cycle-prefs — cycle-prefs.body.invalid_json, cycle-prefs.invalid; disable-coach —
+                disable-coach.body.invalid_json; dawarich — dawarich.credentials_rejected, dawarich.home_place_unknown,
+                dawarich.invalid, dawarich.not_connected, dawarich.rate_limited, dawarich.unreachable; day —
+                day.invalid; demo — demo.readOnly; documents — documents.chat.conversationNotFound,
+                documents.chat.invalid, documents.inbound.alreadyConfirmed, documents.inbound.alreadyPartlyConfirmed,
+                documents.inbound.budgetExceeded, documents.inbound.decryptFailed, documents.inbound.encounterNotFound,
+                documents.inbound.episodeNotFound, documents.inbound.extractFailed, documents.inbound.factNotFound,
+                documents.inbound.factNotPending, documents.inbound.factTypeMismatch, documents.inbound.fileTooLarge,
+                documents.inbound.fileType, documents.inbound.invalidMetadata, documents.inbound.invalidQuery,
+                documents.inbound.invalidUpdate, documents.inbound.localOcrDisabled, documents.inbound.notFound,
+                documents.inbound.notIndexed, documents.inbound.pdfNeedsAnthropic,
+                documents.inbound.providerUnsupported, documents.inbound.quotaExceeded, documents.inbound.rateLimited,
+                documents.inbound.restoreDuplicate, documents.inbound.restoreGone, documents.inbound.sourceAliasLimit,
+                documents.inbound.uploadBusy, documents.inbound.uploadTimeout, documents.inbound.vaccinationNotFound,
+                documents.sources.authRefused, documents.sources.badResponse, documents.sources.browserOnly,
+                documents.sources.invalidAddress, documents.sources.linkTargetNotFound, documents.sources.notConnected,
+                documents.sources.notFound, documents.sources.organizationRequired, documents.sources.originNotAllowed,
                 documents.sources.permissionMissing, documents.sources.rateLimited, documents.sources.redirected,
                 documents.sources.tokenRequired, documents.sources.unavailable, documents.sources.unreachable,
                 documents.sources.versionTooOld; encounter — encounter.invalid, encounter.link.invalid,