polish(pres_mgmt): dark-mode token cleanup on agree/consent forms + style guide update

Replace all forbidden hardcoded colors (red/green bg, text-red-*, text-green-*)
with Skeleton semantic tokens (error/success) so forms render correctly in dark mode.
Update agreement text wrapper from bg-white/dark:bg-gray-900 to bg-surface-50-950.
Document Flowbite Svelte Modal standard pattern (incl. note that classes.footer
padding override does not work in current version).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

documentation/GUIDE__AE_UI_Style_Guidelines.md

@@ -277,7 +277,47 @@ $events_sess.pres_mgmt.session_qr_url[$lq__obj.id] = result; // ← URL string
 
 ---
 
-## 12. Known Issues & Workarounds
+## 12. Flowbite Svelte Modal — Standard Usage
+
+**LLM docs:** [flowbite-svelte.com/llm/components/modal.md](https://flowbite-svelte.com/llm/components/modal.md)
+
+All consent/agreement modals in pres_mgmt use this pattern. Do not deviate.
+
+```svelte
+<Modal
+    title="Person Name — Agreement Title"
+    bind:open={$store.show_modal__thing}
+    autoclose={false}
+    placement="top-center"
+    size="lg">
+
+    <YourFormComponent {prop} />
+
+    {#snippet footer()}
+        <div class="w-full text-center">
+            <button
+                type="button"
+                onclick={() => ($store.show_modal__thing = false)}
+                class="btn preset-tonal-warning border border-warning-500">
+                <X size="1em" class="mr-1" />
+                Close
+            </button>
+        </div>
+    {/snippet}
+</Modal>
+```
+
+**Rules:**
+- `classes` prop, not deprecated `bodyClass`/`headerClass`/`footerClass`
+- **`classes={{ footer: '...' }}` does NOT override footer padding** in the current Flowbite Svelte version — the default `p-4 md:p-5` applies regardless
+- `autoclose={false}` — prevents backdrop click from dismissing the dialog
+- `placement="top-center"` — keeps long forms near the top so content is immediately visible
+- Scrolling inside a long body is **automatic** — never add `max-h` or `overflow` to the body
+- The modal title should include the person's name so the inner component doesn't need a redundant `<h2>`
+
+---
+
+## 13. Known Issues & Workarounds
 
 ### `btn` + `preset-filled-*` resolves to transparent inside `card` components