Security Panel MVP (#1660)

TODOs:

- [x] Add documentation
- [x] e2e tests: run security review, update knowledge, and fix issue
- [x] more stringent risk rating


<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Introduces a new Security mode with a Security Review panel that runs
reviews, edits rules, parses findings via IPC, and supports fixing
issues, with tests and prompt/runtime support.
> 
> - **UI/Preview Panel**:
> - Add `security` preview mode to `previewModeAtom` and ActionHeader
(Shield button).
> - New `SecurityPanel` showing findings table (sorted by severity), run
review, fix issue flow, and edit `SECURITY_RULES.md` dialog.
>   - Wire into `PreviewPanel` content switch.
> - **Hooks**:
>   - `useSecurityReview(appId)`: fetch latest review via IPC.
> - `useStreamChat`: add `onSettled` callback to invoke refreshes after
streams.
> - **IPC/Main**:
> - `security_handlers`: `get-latest-security-review` parses
`<dyad-security-finding>` from latest assistant message.
>   - Register handler in `ipc_host`; expose channel in `preload`.
>   - `ipc_client`: add `getLatestSecurityReview(appId)`.
> - `chat_stream_handlers`: detect `/security-review`, use dedicated
system prompt, optionally append `SECURITY_RULES.md`, suppress
Supabase-not-available note in this mode.
> - **Prompts**:
> - Add `SECURITY_REVIEW_SYSTEM_PROMPT` with structured finding output.
> - **Supabase**:
> - Enhance schema query to include `rls_enabled`, split policy
`using_clause`/`with_check_clause`.
> - **E2E Tests**:
> - New `security_review.spec.ts` plus snapshots and fixture findings;
update test helper for `security` mode and findings table snapshot.
> - Fake LLM server streams security findings for `/security-review` and
increases batch size.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
5022d01e22a2dd929a968eeba0da592e0aeece01. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

e2e-tests/helpers/test_helper.ts

@@ -476,7 +476,9 @@ export class PageObject {
   // Preview panel
   ////////////////////////////////
 
-  async selectPreviewMode(mode: "code" | "problems" | "preview" | "configure") {
+  async selectPreviewMode(
+    mode: "code" | "problems" | "preview" | "configure" | "security",
+  ) {
     await this.page.getByTestId(`${mode}-mode-button`).click();
   }
 
@@ -596,6 +598,12 @@ export class PageObject {
     });
   }
 
+  async snapshotSecurityFindingsTable() {
+    await expect(
+      this.page.getByTestId("security-findings-table"),
+    ).toMatchAriaSnapshot();
+  }
+
   async snapshotServerDump(
     type: "all-messages" | "last-message" | "request" = "all-messages",
     { name = "", dumpIndex = -1 }: { name?: string; dumpIndex?: number } = {},