feat: add TypeBox/Ajv config schema package to the workspace (E00-S04-T01)

Adds packages/config (@personal-blog/config) — the EPPP configuration
service foundation. The package defines the configuration schema with
TypeBox (configSchema: host, port, databaseUrl, sessionSecret — the
validated config fields, golden-tuple pins @sinclair/typebox@0.34.52 and
ajv@8.20.0) and compiles it with Ajv (validateConfig). The environment
adapter (T04), field-specific startup errors (T02) and secret redaction
(T03) build on this boundary in later tasks; nothing reads process.env yet.

Wiring for the new workspace package: lockfile importer + resolved
typebox/ajv tree, apps/server/Dockerfile manifest copy (frozen in-image
install must match the lockfile importers), config-schema CI job, package
set fixtures (workspace-layout, workspace-config, strict-tsconfig,
typescript-pin), probe-file gitignore entry.

packages/config/package.json

@@ -0,0 +1,23 @@
+{
+  "name": "@personal-blog/config",
+  "version": "0.0.0",
+  "private": true,
+  "type": "module",
+  "description": "EPPP configuration service. Owns the TypeBox/Ajv configuration schema (E00-S04-T01); the environment adapter (E00-S04-T04), field-specific startup errors (E00-S04-T02), secret redaction (E00-S04-T03) and the .env.example template (E00-S04-T05) land in later tasks.",
+  "scripts": {
+    "build": "tsc -p tsconfig.json",
+    "typecheck": "tsc -p tsconfig.json --noEmit"
+  },
+  "dependencies": {
+    "@sinclair/typebox": "0.34.52",
+    "ajv": "8.20.0"
+  },
+  "main": "./dist/index.js",
+  "types": "./dist/index.d.ts",
+  "exports": {
+    ".": {
+      "types": "./dist/index.d.ts",
+      "import": "./dist/index.js"
+    }
+  }
+}