refactor(backend): clean up models setup, improve ip utils, add adr docs

- Extract ADR documents for architectural decisions (SQLite, FastAPI, React, APScheduler, Scheduler)
- Refactor setup.py: improve code structure and readability
- Add IP validation utilities with test coverage
- Update frontend components (BanTable, HistoryPage)
- Add pre-commit hooks and CONTRIBUTING.md
- Add .editorconfig for consistent coding standards

frontend/src/components/BanTable.tsx

@@ -241,6 +241,7 @@ export const BanTable = memo(function BanTable({ timeRange, origin, source }: Ba
           items={banItems}
           columns={banColumns}
           getRowId={(item: DashboardBanItem) => `${item.ip}:${item.jail}:${item.banned_at}`}
+          aria-label="Ban records table"
         >
           <DataGridHeader>
             <DataGridRow>

frontend/src/pages/HistoryPage.tsx

@@ -360,6 +360,7 @@ export function HistoryPage(): React.JSX.Element {
             onClick={(): void => {
               setCurrentPage(currentPage - 1);
             }}
+            aria-label="Previous page"
           />
           <Text size={200}>
             Page {String(currentPage)} / {String(totalPages)}
@@ -372,6 +373,7 @@ export function HistoryPage(): React.JSX.Element {
             onClick={(): void => {
               setCurrentPage(currentPage + 1);
             }}
+            aria-label="Next page"
           />
         </div>
       )}