Consolidate audit-fixes branch: webhooks, integrations, and deploy hardening

Batch commit of the pending working tree on security/audit-fixes-2026-07.
Major areas:
- Outbound webhooks / Zapier: schema + signed delivery with retries, public
  v1 API (REST-hook subscribe/unsubscribe), settings UI, cron drain.
- Deploy hardening: email via SMTP2GO (Resend fully removed), verified DB TLS
  (DATABASE_SSL=require + DATABASE_CA), storage fails loud in production when
  Spaces is unconfigured instead of silently using ephemeral disk.
- Integrations & features (concurrent work): accounting (QuickBooks/Xero),
  e-signature (DocuSign/Dropbox Sign), PayPal, geocoding/maps, onboarding,
  expanded legal pages.
- DB migrations 0006–0009.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

lib/db/migrations/0007_chubby_sinister_six.sql

@@ -0,0 +1,19 @@
+CREATE TABLE "signature_requests" (
+	"id" uuid PRIMARY KEY DEFAULT gen_random_uuid() NOT NULL,
+	"user_id" text NOT NULL,
+	"lease_id" uuid,
+	"provider" text NOT NULL,
+	"external_id" text,
+	"status" text DEFAULT 'sent' NOT NULL,
+	"signer_email" text NOT NULL,
+	"signer_name" text,
+	"document_name" text,
+	"signed_document_url" text,
+	"last_error" text,
+	"created_at" timestamp with time zone DEFAULT now() NOT NULL,
+	"completed_at" timestamp with time zone,
+	"updated_at" timestamp with time zone DEFAULT now() NOT NULL
+);
+--> statement-breakpoint
+ALTER TABLE "signature_requests" ADD CONSTRAINT "signature_requests_user_id_profiles_id_fk" FOREIGN KEY ("user_id") REFERENCES "public"."profiles"("id") ON DELETE cascade ON UPDATE no action;--> statement-breakpoint
+ALTER TABLE "signature_requests" ADD CONSTRAINT "signature_requests_lease_id_leases_id_fk" FOREIGN KEY ("lease_id") REFERENCES "public"."leases"("id") ON DELETE set null ON UPDATE no action;