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/0005_large_black_queen.sql

@@ -0,0 +1,17 @@
+CREATE TABLE "accounting_connections" (
+	"id" uuid PRIMARY KEY DEFAULT gen_random_uuid() NOT NULL,
+	"user_id" text NOT NULL,
+	"provider" text NOT NULL,
+	"access_token" text NOT NULL,
+	"refresh_token" text NOT NULL,
+	"expires_at" timestamp with time zone,
+	"realm_id" text,
+	"org_name" text,
+	"status" text DEFAULT 'active' NOT NULL,
+	"last_sync_at" timestamp with time zone,
+	"last_error" text,
+	"created_at" timestamp with time zone DEFAULT now() NOT NULL,
+	"updated_at" timestamp with time zone DEFAULT now() NOT NULL
+);
+--> statement-breakpoint
+ALTER TABLE "accounting_connections" ADD CONSTRAINT "accounting_connections_user_id_profiles_id_fk" FOREIGN KEY ("user_id") REFERENCES "public"."profiles"("id") ON DELETE cascade ON UPDATE no action;