feat: leads capture API with PostgreSQL backend

Bun + Hono API service for capturing email subscribers across
multiple projects. Supports subscribe/unsubscribe, admin stats,
and deduplication per email+project pair.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

bun.lock

@@ -0,0 +1,18 @@
+{
+  "lockfileVersion": 1,
+  "configVersion": 1,
+  "workspaces": {
+    "": {
+      "name": "leads-api",
+      "dependencies": {
+        "hono": "^4",
+        "postgres": "^3",
+      },
+    },
+  },
+  "packages": {
+    "hono": ["hono@4.12.2", "", {}, "sha512-gJnaDHXKDayjt8ue0n8Gs0A007yKXj4Xzb8+cNjZeYsSzzwKc0Lr+OZgYwVfB0pHfUs17EPoLvrOsEaJ9mj+Tg=="],
+
+    "postgres": ["postgres@3.4.8", "", {}, "sha512-d+JFcLM17njZaOLkv6SCev7uoLaBtfK86vMUXhW1Z4glPWh4jozno9APvW/XKFJ3CCxVoC7OL38BqRydtu5nGg=="],
+  }
+}