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

bun.lock

@@ -5,10 +5,10 @@
       "name": "pokeshare",
       "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",
       },
     },
@@ -78,6 +78,8 @@
 
     "@clack/prompts": ["@clack/prompts@1.7.0", "", { "dependencies": { "@clack/core": "1.4.3", "fast-string-width": "^3.0.2", "fast-wrap-ansi": "^0.2.0", "sisteransi": "^1.0.5" } }, "sha512-y7/yvZ2TPAnR9+jnc00klvNNLkJiXFFrQA/hlLCcxA9a2A4zQIOimyFQ9XfwYKiGD1fb5GY8vbKIIgO8d5Tb2A=="],
 
+    "@directus/sdk": ["@directus/sdk@23.0.0", "", {}, "sha512-hoPSj9bhe2dxaq9PXuvqqCHzjy9sUvcik2vi5DA/xKZ7E42O2TgDfNgRjYY8gb0ZOkm3TAUeLuEKf4aJTrUYIw=="],
+
     "@emnapi/core": ["@emnapi/core@1.11.1", "", { "dependencies": { "@emnapi/wasi-threads": "1.2.2", "tslib": "^2.4.0" } }, "sha512-RSvbQmHzdKzNsLYa/wHrbc3KN4sYLKAdPZxqiM2HATqv/SBk2/ENSHpvXGaLOMcsAyz0poEGqkmmKYG3OWiJEQ=="],
 
     "@emnapi/runtime": ["@emnapi/runtime@1.11.1", "", { "dependencies": { "tslib": "^2.4.0" } }, "sha512-vgj7R3y3Wgx24IQaGPA/R6YFXLHVMOZ0uVEyIQPaWs+rd1AzfEMXlAC22FYwO1XkKR6NPsq7mUandH8oIRdZFw=="],
@@ -556,8 +558,6 @@
 
     "picomatch": ["picomatch@4.0.5", "", {}, "sha512-RvwwcruNjI1ncT5xRakeyS9Lf8lcItv34KD+aif+VH9kduAyfYBipGh12274xtenIPZ119/R9BdTBa8gAwSh0A=="],
 
-    "pocketbase": ["pocketbase@0.27.0", "", {}, "sha512-K5N6d93UP/BNMbMnlZ6BUfy9VPCIvLyqhJFOsNI8OsZwzvKWEAfyD36boi5K4ECIOl5HMlo0TzuaeGdKpMwizQ=="],
-
     "postcss": ["postcss@8.5.23", "", { "dependencies": { "nanoid": "^3.3.16", "picocolors": "^1.1.1", "source-map-js": "^1.2.1" } }, "sha512-g50586zr4bZmwFiTlflMu8E0bDTb5I5gertgwAKmsdUlTQIhZtunzUlD1WSzwcVWPoAVpsrA6vlfCD7oXvRwgg=="],
 
     "prismjs": ["prismjs@1.30.0", "", {}, "sha512-DEvV2ZF2r2/63V+tK8hQvrR2ZGn10srHbXviTlcv7Kpzw8jWiNTqbVgjO3IY8RxrrOUF8VPMQQFysYYYv0YZxw=="],