feat(store): migration 017 -- private RLS-scoped uploaded_transcripts (ADR-033)

Separate table, not a user_id on the shared transcripts (ADR-021). ENABLE +
FORCE ROW LEVEL SECURITY with the migration-003 policy, user_id NOT NULL
ON DELETE CASCADE, typed error_kind, per-row serving endpoint, JSONB segments.
CHECK constraints: done => content, failed => error_kind.

Up and down are one commit: golang-migrate pairs them.

Mutation-checked: dropping FORCE, the policy, or the cascade each turn a test
red. FORCE is only observable structurally -- the app role is not the table
owner, so no behavioural test can see it.

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

internal/adapters/store/migrations/017_uploaded_transcripts.down.sql

@@ -0,0 +1,3 @@
+-- Drops the private uploaded-transcript store and every transcript in it. There
+-- is no revert of the data: the original audio was never kept (ADR-033).
+DROP TABLE uploaded_transcripts;

internal/adapters/store/migrations/017_uploaded_transcripts.up.sql

@@ -0,0 +1,48 @@
+-- Migration 017: uploaded_transcripts — PRIVATE transcripts of audio a user
+-- uploaded themselves (ADR-033, tapir#33).
+--
+-- This is deliberately NOT the shared `transcripts` table (migration 015,
+-- ADR-021). That table is non-RLS on the explicit grounds that it holds only
+-- public caption content and nothing user-identifying. A recorded meeting is the
+-- opposite: private third-party content owned by exactly one user. Reusing
+-- `transcripts` — or adding a user_id to it with a partial policy — would put a
+-- private row in the one table the isolation test asserts is shared, and would
+-- pass CI green. A separate table keeps ADR-021's exception singular.
+--
+-- Row-level security follows migration 003 exactly: ENABLE + FORCE (the app
+-- connects as the table owner, which bypasses RLS unless forced), and a policy
+-- keyed off the per-request GUC tapir.current_user_id. With no GUC set the
+-- predicate is NULL and the table is deny-all.
+--
+-- The original audio is never stored (ADR-033): this row is all that is kept.
+-- segments holds the timestamped cues; re-transcribing 90 minutes costs ~7
+-- minutes, so discarding the timestamps would be irreversible.
+CREATE TABLE uploaded_transcripts (
+    id            UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    user_id       UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    title         TEXT NOT NULL,
+    status        TEXT NOT NULL DEFAULT 'queued'
+                  CHECK (status IN ('queued', 'transcribing', 'done', 'failed')),
+    content       TEXT,
+    segments      JSONB,
+    endpoint      TEXT,             -- which backend served it (iguana | berget); a quality fact
+    audio_seconds DOUBLE PRECISION,
+    error_kind    TEXT,             -- typed, never a provider's error string (ADR-033)
+    created_at    TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+    finished_at   TIMESTAMPTZ,
+    CONSTRAINT uploaded_transcripts_done_has_content
+        CHECK (status <> 'done' OR content IS NOT NULL),
+    CONSTRAINT uploaded_transcripts_failed_has_error_kind
+        CHECK (status <> 'failed' OR error_kind IS NOT NULL)
+);
+
+CREATE INDEX idx_uploaded_transcripts_user ON uploaded_transcripts (user_id, created_at DESC);
+
+ALTER TABLE uploaded_transcripts ENABLE ROW LEVEL SECURITY;
+ALTER TABLE uploaded_transcripts FORCE ROW LEVEL SECURITY;
+CREATE POLICY uploaded_transcripts_isolation ON uploaded_transcripts
+    FOR ALL
+    USING (user_id = current_setting('tapir.current_user_id', true)::uuid);
+
+COMMENT ON TABLE uploaded_transcripts IS
+    'PRIVATE per-user transcripts of user-supplied audio. RLS-scoped (ADR-012). Never merge into the shared transcripts table (ADR-021, ADR-033).';