feat(uploads): choose the language of a recording; record it, show it, carry it to the engines (#61)

Form field (Swedish preselected, Other = auto) read before the file part and refused
before anything is spooled if outside the closed set; stored on the row (migration 021,
CHECK constraint, default sv for history); carried on the Job and the worker's context;
shown on the status page. Feature scenarios and the coverage map are updated, and
ADR-033/034 amended.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

test/acceptance/scenario_coverage_test.go

@@ -123,6 +123,10 @@ var scenarioCoverage = map[string]string{
 	"A long recording is not cut to its first third":                            "TestAnswerMaxCharsOverridesTheServiceCap",
 
 	"A transcript made by the cloud fallback says the audio left the homelab": "TestUploadStatus_ACloudServedTranscriptSaysTheAudioLeftTheHomelab",
+	"I choose the language of a recording":                                    "TestUploadPost_TheLanguageFieldReachesTheJobAndTheRow",
+	"Swedish stays the default":                                               "TestUploadPost_NoLanguageFieldIsSwedishAsBefore",
+	"A language outside the list is refused":                                  "TestUploadPost_ALanguageOutsideTheClosedSetIsRefusedBeforeAnythingIsSpooledOrStored",
+	"A recording in another language never reaches the Swedish-only engine":   "TestEnsemble_AnAutoLanguageUploadNeverReachesTheBaseEngineAndIsNotReconciled",
 
 	"I can delete a finished recording":                        "TestUploadDelete_AnOwnerRemovesAFinishedOrFailedRecordingAndLandsOnTheList",
 	"A recording still being transcribed cannot be deleted":    "TestUploadDelete_ARecordingStillBeingTranscribedIsRefusedWith409AndKept",