docs(api-reference): align API docs and openapi schema with v3 spec

- create-memory-export.mdx: replace `session_id` filter with `app_id`
  (spec: /v1/exports/ filters = user_id, agent_id, app_id, run_id)
- get-memory-export.mdx: replace stale filter list (session_id removed)
  with correct fields: user_id, agent_id, app_id, run_id, created_at, updated_at
- search-memories.mdx: fix comparison table — rerank V1/V2 default was
  `true`, spec shows `false`; threshold V1 is absent (not "No default"),
  V2 default is 0.3 (not absent)
- organizations-projects.mdx: rewrite Key Capabilities bullet — org/project
  are NOT init params; they resolve automatically from the API key via /v1/ping/
- openapi.json DELETE /v1/batch/: fix request schema from {memory_ids:[uuid]}
  to {memories:[{memory_id:uuid}]} to match Python client.batch_delete()
- openapi.json PUT /v1/batch/: make `text` optional (remove from required),
  add optional `metadata` property — matches Python client.batch_update() docstring

docs/api-reference/memory/search-memories.mdx

@@ -23,8 +23,8 @@ The `filters` object supports complex logical operations (AND, OR, NOT) and comp
 | Parameter | V1/V2 | V3 |
 | --- | --- | --- |
 | `top_k` | Supported (default 10) | Supported (1-1000, default 10) |
-| `threshold` | No default | Default `0.1` (pass `0.0` to disable) |
-| `rerank` | Default `true` | Default `false` (pass `true` to enable) |
+| `threshold` | V1: not supported / V2: default `0.3` | Default `0.1` (pass `0.0` to disable) |
+| `rerank` | Default `false` | Default `false` (pass `true` to enable) |
 
 <CodeGroup>
 ```python Platform API Example