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>

internal/adapters/store/migrations/021_uploaded_transcripts_language.up.sql

@@ -0,0 +1,13 @@
+-- Migration 021: the language an upload is transcribed as (tapir#61).
+--
+-- 'sv'   Swedish: the engines are sent language=sv. Every row before this migration was
+--        transcribed that way (the request hard-coded it), so the default is true history.
+-- 'auto' Other: the engine detects the language and the Swedish-only engine is not used.
+--
+-- A closed set held by the table as well as by the form and the request code, so a second
+-- writer or a bug cannot store a value the engines are never meant to receive. The column
+-- sits on the already-FORCE'd, RLS-scoped uploaded_transcripts, so the exact-set isolation
+-- test is unaffected.
+ALTER TABLE uploaded_transcripts
+    ADD COLUMN language TEXT NOT NULL DEFAULT 'sv'
+        CONSTRAINT uploaded_transcripts_language_check CHECK (language IN ('sv', 'auto'));