Restructure Core management into linkable routes and add common layout navigation

- Renamed person route to people for consistency
- Refactored /core dashboard to use standard <a> links
- Added common management <nav> to core layout
- Replaced goto() with standard links across all list and detail pages
- Fixed 500 error caused by broken import path and strict layout data

src/routes/core/accounts/+page.svelte

@@ -117,9 +117,9 @@
                                 {/if}
                             </td>
                             <td class="text-right">
-                                <button class="btn btn-sm variant-soft-primary" onclick={() => goto(`/core/accounts/${acct.account_id_random}`)}>
+                                <a class="btn btn-sm variant-soft-primary" href="/core/accounts/{acct.account_id_random}">
                                     Manage
-                                </button>
+                                </a>
                             </td>
                         </tr>
                     {/each}