docs(ui): add BLUEPRINT, QUIRKS, blockers dir

Co-authored-by: yuneng-jiang <yuneng-berri@users.noreply.github.com>

ui/litellm-dashboard/docs/BLUEPRINT.md

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+# Phase 1 migration blueprint
+
+This document is finalized after Section 1 (Access Groups) and locked for the
+rest of the phase-1 run. Later sections follow the patterns defined here; any
+deviation is logged in `DEVIATIONS.md`.
+
+**Status:** Not yet locked — will be drafted during Section 1 (Access Groups).
+
+Once locked, this file will contain:
+
+1. **Component translation table** — every antd component → shadcn primitive,
+   with import paths and any prop-shape differences.
+2. **Icon translation table** — @ant-design/icons, @heroicons/react,
+   @remixicon/react → lucide-react (only).
+3. **Toast pattern** — before/after code example using the
+   `MessageManager` / `NotificationManager` bridges (which now delegate to
+   sonner under the hood).
+4. **Form pattern** — canonical shadcn `<Form>` + `react-hook-form` + `zod`
+   example, including schema location, `FormField` / `FormItem` / `FormLabel`
+   / `FormControl` / `FormDescription` / `FormMessage` wiring, and submit
+   handler hooked into the existing data-layer function.
+5. **Table pattern** — shadcn `<Table>` + `@tanstack/react-table` with
+   sort / filter / pagination. Column-visibility UI if used.
+6. **Shared layout patterns** — page header, section card, empty state,
+   loading skeleton, error alert, permissions gate.

ui/litellm-dashboard/docs/QUIRKS.md

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+# Current-UI quirks observed during migration
+
+Format per entry:
+
+## <section> — <short title>
+
+- **Observed in:** `<path>:<line>` (or route URL + screenshot reference)
+- **Current behavior:** what the UI does today.
+- **Suspected issue:** why this looks wrong.
+- **Resolution:** `preserve` | `fix`
+- **Rationale:** one-line justification for the resolution.
+- **Parity spec impact:** `none` | "skip old-UI sanity check for assertion X".