Add public AI prompt templates for websites.

Manage reusable templates in Super Admin, attach editable per-site prompts with Meshkee API public links that require no auth.

Co-authored-by: Cursor <cursoragent@cursor.com>

database/migrations/075_ai_prompt_templates.sql

@@ -0,0 +1,32 @@
+-- Super Admin AI prompt templates (per website / domain), with public share ids.
+
+CREATE TABLE IF NOT EXISTS ai_prompt_templates (
+  id          BIGSERIAL PRIMARY KEY,
+  domain_id   BIGINT NOT NULL REFERENCES domains (id) ON DELETE CASCADE,
+  name        VARCHAR(255) NOT NULL,
+  body        TEXT NOT NULL,
+  public_id   VARCHAR(32) NOT NULL,
+  created_at  TIMESTAMPTZ NOT NULL DEFAULT now(),
+  updated_at  TIMESTAMPTZ NOT NULL DEFAULT now(),
+  CONSTRAINT ai_prompt_templates_public_id_unique UNIQUE (public_id)
+);
+
+CREATE INDEX IF NOT EXISTS idx_ai_prompt_templates_domain_id
+  ON ai_prompt_templates (domain_id);
+
+CREATE INDEX IF NOT EXISTS idx_ai_prompt_templates_created_at
+  ON ai_prompt_templates (created_at DESC);
+
+CREATE OR REPLACE FUNCTION ai_prompt_templates_set_updated_at()
+RETURNS TRIGGER AS $$
+BEGIN
+  NEW.updated_at = now();
+  RETURN NEW;
+END;
+$$ LANGUAGE plpgsql;
+
+DROP TRIGGER IF EXISTS ai_prompt_templates_set_updated_at ON ai_prompt_templates;
+CREATE TRIGGER ai_prompt_templates_set_updated_at
+  BEFORE UPDATE ON ai_prompt_templates
+  FOR EACH ROW
+  EXECUTE FUNCTION ai_prompt_templates_set_updated_at();