feat(properties): add parent_id for sub-property hierarchy

Phase 1 of the parent/child rollup feature. Self-FK on properties
with ON DELETE RESTRICT, plus a CHECK that blocks self-reference at
the DB level. Service-layer helpers (getDescendantIds,
getAncestorIds, assertNoCycle) walk the tree via recursive CTEs and
guard against cycles and cross-company parents. softDeleteProperty
now refuses to delete a property with live children.

No UI yet — readers and roll-up routes land in Phase 2.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

drizzle/0016_property_parent_id.sql

@@ -0,0 +1,3 @@
+ALTER TABLE "properties" ADD COLUMN "parent_id" uuid;--> statement-breakpoint
+ALTER TABLE "properties" ADD CONSTRAINT "properties_parent_id_properties_id_fk" FOREIGN KEY ("parent_id") REFERENCES "public"."properties"("id") ON DELETE restrict ON UPDATE no action;--> statement-breakpoint
+CREATE INDEX "properties_by_parent" ON "properties" USING btree ("company_id","parent_id");

drizzle/0017_property_parent_check.sql

@@ -0,0 +1,7 @@
+-- A property cannot be its own parent. Deeper cycle prevention (e.g.
+-- A→B→A) is enforced in the service layer because Postgres can't express
+-- recursive CHECK constraints; the assertNoCycle helper in
+-- src/lib/server/services/properties.ts walks ancestors before save.
+ALTER TABLE "properties"
+  ADD CONSTRAINT "properties_parent_not_self"
+  CHECK (parent_id IS NULL OR parent_id <> id);

drizzle/meta/_journal.json

@@ -113,6 +113,20 @@
       "when": 1776932900000,
       "tag": "0015_expenses_updated_at_trigger",
       "breakpoints": true
+    },
+    {
+      "idx": 16,
+      "version": "7",
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+      "tag": "0016_property_parent_id",
+      "breakpoints": true
+    },
+    {
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+      "version": "7",
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+      "tag": "0017_property_parent_check",
+      "breakpoints": true
     }
   ]
 }