feat: filter meaningful conversations with local model

migrations/000044_conversation_content_assessment.down.sql

@@ -0,0 +1,5 @@
+BEGIN;
+
+DROP TABLE IF EXISTS conversation_content_assessment;
+
+COMMIT;

migrations/000044_conversation_content_assessment.up.sql

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+BEGIN;
+
+CREATE TABLE conversation_content_assessment (
+    id                  uuid PRIMARY KEY DEFAULT gen_random_uuid(),
+    public_id           uuid NOT NULL UNIQUE DEFAULT gen_random_uuid(),
+    tenant_id           uuid NOT NULL REFERENCES tenant(id),
+    subject_id          uuid NOT NULL,
+    conversation_id     uuid NOT NULL,
+    generation_version  bigint NOT NULL CHECK (generation_version > 0),
+    meaningful          boolean NOT NULL,
+    story_worthy        boolean NOT NULL,
+    decision_reason     varchar(500) NOT NULL CHECK (length(decision_reason) > 0),
+    model_ref           varchar(160) NOT NULL,
+    prompt_version      varchar(80) NOT NULL,
+    confidence          numeric(5,4) NOT NULL CHECK (confidence BETWEEN 0 AND 1),
+    created_at          timestamptz NOT NULL DEFAULT now(),
+    CONSTRAINT conversation_content_assessment_decision_check CHECK (meaningful OR NOT story_worthy),
+    CONSTRAINT conversation_content_assessment_conversation_tenant_fk FOREIGN KEY (conversation_id, tenant_id)
+        REFERENCES conversation (id, tenant_id),
+    CONSTRAINT conversation_content_assessment_subject_tenant_fk FOREIGN KEY (subject_id, tenant_id)
+        REFERENCES subject_profile (id, tenant_id),
+    CONSTRAINT conversation_content_assessment_generation_key UNIQUE (conversation_id, generation_version)
+);
+
+CREATE INDEX conversation_content_assessment_conversation_idx
+    ON conversation_content_assessment (conversation_id, generation_version DESC);
+
+COMMIT;