Migrate backend from PocketBase to Directus

Full cutover: auth, users, collection and friendships now run on Directus
via @directus/sdk, with owner/visibility rules enforced by Directus
permissions.

- middleware: Directus session (directus_auth cookie) with token refresh
- /login is Directus (email normalized to lowercase), new /register page
  (first/last name, username) backed by public registration
- collection, friends and profile pages + all API endpoints ported;
  ownership and addressee-only accept/decline enforced by permissions
- display names use first_name/last_name everywhere (nav, friends, profile)
- PocketBase SDK, POCKETBASE_URL and pb_schema.json removed
- README and compose updated for DIRECTUS_URL

package-lock.json

@@ -9,10 +9,10 @@
       "version": "0.0.1",
       "dependencies": {
         "@astrojs/node": "^11.0.2",
+        "@directus/sdk": "^23.0.0",
         "@tailwindcss/vite": "^4.3.3",
         "astro": "^7.1.3",
         "basecoat-css": "^1.0.2",
-        "pocketbase": "^0.27.0",
         "tailwindcss": "^4.3.3"
       },
       "engines": {
@@ -492,6 +492,18 @@
         "node": ">= 20.12.0"
       }
     },
+    "node_modules/@directus/sdk": {
+      "version": "23.0.0",
+      "resolved": "https://registry.npmjs.org/@directus/sdk/-/sdk-23.0.0.tgz",
+      "integrity": "sha512-hoPSj9bhe2dxaq9PXuvqqCHzjy9sUvcik2vi5DA/xKZ7E42O2TgDfNgRjYY8gb0ZOkm3TAUeLuEKf4aJTrUYIw==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=22"
+      },
+      "funding": {
+        "url": "https://github.com/directus/directus?sponsor=1"
+      }
+    },
     "node_modules/@emnapi/core": {
       "version": "1.11.3",
       "resolved": "https://registry.npmjs.org/@emnapi/core/-/core-1.11.3.tgz",
@@ -3676,10 +3688,6 @@
         "url": "https://github.com/sponsors/jonschlinkert"
       }
     },
-    "node_modules/pocketbase": {
-      "version": "0.27.0",
-      "license": "MIT"
-    },
     "node_modules/postcss": {
       "version": "8.5.23",
       "funding": [