Deploy on DigitalOcean App Platform (GitHub-source build) + consolidate audit-fixes

Deploy config:
- .do/app.yaml: build the Dockerfile directly from GitHub (deploy_on_push) instead
  of a pre-built DOCR image; NEXT_PUBLIC_* set RUN_AND_BUILD_TIME with the
  propertymanagement.network domain so they bake into the client bundle; add
  custom domains block (apex + www); wire Sentry DSN (server + browser).

Included pending work from the audit-fixes branch:
- AI provider abstraction (OpenAI/Anthropic, admin-selectable; Anthropic default)
- Per-landlord e-signature (DocuSign OAuth + Dropbox Sign) + migration 0010
- Outbound webhooks / Zapier integration
- PayPal removal (Stripe-only billing)
- Storage hardening (fail-loud when Spaces unconfigured), security fixes

Verified: full production Docker build (same build-args as DO) passes clean.

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

lib/db/migrations/0010_esign_connections.sql

@@ -0,0 +1,17 @@
+CREATE TABLE "esign_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,
+	"expires_at" timestamp with time zone,
+	"account_id" text,
+	"base_uri" text,
+	"account_name" text,
+	"status" text DEFAULT 'active' NOT NULL,
+	"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 "esign_connections" ADD CONSTRAINT "esign_connections_user_id_profiles_id_fk" FOREIGN KEY ("user_id") REFERENCES "public"."profiles"("id") ON DELETE cascade ON UPDATE no action;