feat(20-01): add migration 0009_client_transcripts.sql

DDL for client_transcripts table: id (nanoid PK), lead_id/client_id
(nullable FKs with ON DELETE CASCADE), title, content (NOT NULL),
call_date (date NOT NULL), created_at (timestamptz). Three indexes on
lead_id, client_id, call_date DESC. APPLY TO PROD via SSH before
pushing schema-dependent code (Plan 20-02/20-03).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/db/migrations/0009_client_transcripts.sql

@@ -0,0 +1,22 @@
+-- Phase 20: Knowledge Base Cliente — tabella transcript datati per lead/cliente
+-- Additive only. No drops/truncates (Data Safety LOCKED).
+-- Applicare a prod via SSH tunnel PRIMA di pushare il codice dipendente (D-03).
+
+CREATE TABLE IF NOT EXISTS client_transcripts (
+  id          text PRIMARY KEY NOT NULL,
+  lead_id     text REFERENCES leads(id) ON DELETE CASCADE,
+  client_id   text REFERENCES clients(id) ON DELETE CASCADE,
+  title       text,
+  content     text NOT NULL,
+  call_date   date NOT NULL,
+  created_at  timestamp with time zone NOT NULL DEFAULT now()
+);
+
+CREATE INDEX IF NOT EXISTS client_transcripts_lead_id_idx
+  ON client_transcripts (lead_id);
+
+CREATE INDEX IF NOT EXISTS client_transcripts_client_id_idx
+  ON client_transcripts (client_id);
+
+CREATE INDEX IF NOT EXISTS client_transcripts_call_date_idx
+  ON client_transcripts (call_date DESC);