fix(api): rename 'metadata' to 'response_metadata' to avoid Pydantic conflict

The field name 'metadata' conflicts with Pydantic's internal ClassVar.
Renamed to 'response_metadata' throughout:
- Backend: RoutineSuggestion, BatchSuggestion, ShoppingSuggestionResponse
- Frontend: TypeScript types and component usages

This fixes the AttributeError when setting metadata on SQLModel instances.

frontend/src/lib/types.ts

@@ -263,7 +263,7 @@ export interface RoutineSuggestion {
   // Phase 3: Observability fields
   validation_warnings?: string[];
   auto_fixes_applied?: string[];
-  metadata?: ResponseMetadata;
+  response_metadata?: ResponseMetadata;
 }
 
 export interface DayPlan {
@@ -279,7 +279,7 @@ export interface BatchSuggestion {
   // Phase 3: Observability fields
   validation_warnings?: string[];
   auto_fixes_applied?: string[];
-  metadata?: ResponseMetadata;
+  response_metadata?: ResponseMetadata;
 }
 
 // ─── Shopping suggestion types ───────────────────────────────────────────────
@@ -300,7 +300,7 @@ export interface ShoppingSuggestionResponse {
   // Phase 3: Observability fields
   validation_warnings?: string[];
   auto_fixes_applied?: string[];
-  metadata?: ResponseMetadata;
+  response_metadata?: ResponseMetadata;
 }
 
 // ─── Health types ────────────────────────────────────────────────────────────

frontend/src/routes/products/suggest/+page.svelte

@@ -20,7 +20,7 @@
 	// Phase 3: Observability state
 	let validationWarnings = $state<string[] | undefined>(undefined);
 	let autoFixes = $state<string[] | undefined>(undefined);
-	let metadata = $state<ResponseMetadata | undefined>(undefined);
+	let responseMetadata = $state<ResponseMetadata | undefined>(undefined);
 
 	function enhanceForm() {
 		loading = true;
@@ -33,7 +33,7 @@
 				// Phase 3: Extract observability data
 				validationWarnings = result.data.validation_warnings as string[] | undefined;
 				autoFixes = result.data.auto_fixes_applied as string[] | undefined;
-				metadata = result.data.metadata as ResponseMetadata | undefined;
+				responseMetadata = result.data.response_metadata as ResponseMetadata | undefined;
 				errorMsg = null;
 			} else if (result.type === 'failure') {
 				errorMsg = (result.data?.error as string) ?? m["suggest_errorDefault"]();
@@ -93,11 +93,11 @@
 			{#if validationWarnings}
 				<ValidationWarningsAlert warnings={validationWarnings} />
 			{/if}
-			{#if metadata?.reasoning_chain}
-				<ReasoningChainViewer reasoningChain={metadata.reasoning_chain} />
+			{#if responseMetadata?.reasoning_chain}
+				<ReasoningChainViewer reasoningChain={responseMetadata.reasoning_chain} />
 			{/if}
-			{#if metadata}
-				<MetadataDebugPanel {metadata} />
+			{#if responseMetadata}
+				<MetadataDebugPanel metadata={responseMetadata} />
 			{/if}
 		</div>
 

frontend/src/routes/routines/suggest/+page.svelte

@@ -227,11 +227,11 @@
 					{#if suggestion.validation_warnings}
 						<ValidationWarningsAlert warnings={suggestion.validation_warnings} />
 					{/if}
-					{#if suggestion.metadata?.reasoning_chain}
-						<ReasoningChainViewer reasoningChain={suggestion.metadata.reasoning_chain} />
+					{#if suggestion.response_metadata?.reasoning_chain}
+						<ReasoningChainViewer reasoningChain={suggestion.response_metadata.reasoning_chain} />
 					{/if}
-					{#if suggestion.metadata}
-						<MetadataDebugPanel metadata={suggestion.metadata} />
+					{#if suggestion.response_metadata}
+						<MetadataDebugPanel metadata={suggestion.response_metadata} />
 					{/if}
 
 					<!-- Steps -->
@@ -349,11 +349,11 @@
 					{#if batch.validation_warnings}
 						<ValidationWarningsAlert warnings={batch.validation_warnings} />
 					{/if}
-					{#if batch.metadata?.reasoning_chain}
-						<ReasoningChainViewer reasoningChain={batch.metadata.reasoning_chain} />
+					{#if batch.response_metadata?.reasoning_chain}
+						<ReasoningChainViewer reasoningChain={batch.response_metadata.reasoning_chain} />
 					{/if}
-					{#if batch.metadata}
-						<MetadataDebugPanel metadata={batch.metadata} />
+					{#if batch.response_metadata}
+						<MetadataDebugPanel metadata={batch.response_metadata} />
 					{/if}
 
 					<!-- Day cards -->