Add Zod validation layer and AI blog generation

Introduce a schema-first validation layer and an AI blog generation
feature, plus one-command Cloudflare provisioning.

- src/schemas/ holds Zod input schemas for post, content, case,
  settings, AI, and keywords; parseForm() in src/lib/form.ts validates
  FormData and returns per-field errors.
- Migrate all admin POST handlers to parseForm, showing field-level
  errors and only redirecting once validation passes.
- Add blog_keywords table and posts.focus_keyword (migration 0002);
  uniqueSlug() centralised in src/data/content.ts.
- Add src/lib/ai.ts (OpenAI-compatible chat completions + optional
  Tavily research) and /admin/ai for AI settings, keyword queue, and
  draft generation.
- Add scripts/setup.mjs (npm run setup) to provision D1/KV, set
  secrets, and optionally migrate, seed, and deploy.
- Document AI secrets, Workers Builds deploy flow, and new schemas
  across README and AGENTS docs.

src/pages/admin/cases.astro

@@ -4,11 +4,17 @@ import AdminLayout from "../../layouts/AdminLayout.astro";
 import { cases } from "../../db/schema";
 import { getDb } from "../../lib/db";
 import { getEnv } from "../../lib/env";
+import { parseForm } from "../../lib/form";
+import { caseInput } from "../../schemas";
 
 export const prerender = false;
 
 const db = getDb(getEnv().DB);
 
+let errors: Record<string, string> = {};
+let failedId = "";
+let failedAdd = false;
+
 function str(form: FormData, key: string): string {
   return String(form.get(key) ?? "").trim();
 }
@@ -17,36 +23,40 @@ if (Astro.request.method === "POST") {
   const form = await Astro.request.formData();
   const action = str(form, "action");
 
-  if (action === "add") {
-    const title = str(form, "title");
-    if (title) {
+  if (action === "add" || action === "save") {
+    const parsed = parseForm(form, caseInput);
+    if (!parsed.ok) {
+      errors = parsed.errors;
+      failedId = str(form, "id");
+      failedAdd = action === "add";
+    } else if (action === "add") {
       const [row] = await db.select({ m: max(cases.sortOrder) }).from(cases);
       await db.insert(cases).values({
         id: crypto.randomUUID(),
-        title,
-        location: str(form, "location") || null,
-        completedAt: str(form, "completedAt") || null,
-        description: str(form, "description") || null,
-        imageUrl: str(form, "imageUrl") || null,
+        title: parsed.data.title,
+        location: parsed.data.location || null,
+        completedAt: parsed.data.completedAt || null,
+        description: parsed.data.description || null,
+        imageUrl: parsed.data.imageUrl || null,
         sortOrder: (row?.m ?? 0) + 1,
-        status: str(form, "status") === "draft" ? "draft" : "published",
+        status: parsed.data.status,
         updatedAt: new Date(),
       });
+    } else {
+      const id = str(form, "id");
+      await db
+        .update(cases)
+        .set({
+          title: parsed.data.title,
+          location: parsed.data.location || null,
+          completedAt: parsed.data.completedAt || null,
+          description: parsed.data.description || null,
+          imageUrl: parsed.data.imageUrl || null,
+          status: parsed.data.status,
+          updatedAt: new Date(),
+        })
+        .where(eq(cases.id, id));
     }
-  } else if (action === "save") {
-    const id = str(form, "id");
-    await db
-      .update(cases)
-      .set({
-        title: str(form, "title"),
-        location: str(form, "location") || null,
-        completedAt: str(form, "completedAt") || null,
-        description: str(form, "description") || null,
-        imageUrl: str(form, "imageUrl") || null,
-        status: str(form, "status") === "draft" ? "draft" : "published",
-        updatedAt: new Date(),
-      })
-      .where(eq(cases.id, id));
   } else if (action === "delete") {
     await db.delete(cases).where(eq(cases.id, str(form, "id")));
   } else if (action === "up" || action === "down") {
@@ -68,7 +78,9 @@ if (Astro.request.method === "POST") {
     }
   }
 
-  return Astro.redirect("/admin/cases");
+  if (Object.keys(errors).length === 0) {
+    return Astro.redirect("/admin/cases");
+  }
 }
 
 const list = await db.select().from(cases).orderBy(asc(cases.sortOrder));
@@ -85,6 +97,7 @@ const list = await db.select().from(cases).orderBy(asc(cases.sortOrder));
       <div class="grid2">
         <div>
           <label for="a-title">標題</label>
+          {failedAdd && errors.title && <span class="field-error">{errors.title}</span>}
           <input id="a-title" name="title" type="text" required placeholder="例：大埔上碗窯 — 雙玻光伏板" />
         </div>
         <div>
@@ -119,6 +132,7 @@ const list = await db.select().from(cases).orderBy(asc(cases.sortOrder));
             <div class="grid2">
               <div>
                 <label>標題</label>
+                {failedId === item.id && errors.title && <span class="field-error">{errors.title}</span>}
                 <input name="title" type="text" value={item.title} required />
               </div>
               <div>