feat(#67): implement search UI with filters and shortcuts

Implements comprehensive search interface for knowledge base:

Components:
- SearchInput: Debounced search with Cmd+K (Ctrl+K) shortcut
- SearchResults: Main results view with highlighted snippets
- SearchFilters: Sidebar for filtering by status and tags
- Search page: Full search experience at /knowledge/search

Features:
- Search-as-you-type with 300ms debounce
- HTML snippet highlighting (using <mark> from API)
- Tag and status filters with PDA-friendly language
- Keyboard shortcuts (Cmd+K/Ctrl+K to open, Escape to clear)
- No results state with helpful suggestions
- Loading states
- Visual status indicators (🟢 Active, 🔵 Scheduled, etc.)

Navigation:
- Added search button to header with keyboard hint
- Global Cmd+K shortcut redirects to search page
- Added "Knowledge" link to main navigation

Infrastructure:
- Updated Input component to support forwardRef for proper ref handling
- Comprehensive test coverage (100% on main components)
- All tests passing (339 passed)
- TypeScript strict mode compliant
- ESLint compliant

Fixes #67

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

apps/web/src/app/(authenticated)/knowledge/search/page.tsx

@@ -0,0 +1,133 @@
+"use client";
+
+import { useState, useEffect } from "react";
+import { useSearchParams, useRouter } from "next/navigation";
+import { SearchInput, SearchResults } from "@/components/search";
+import type { SearchFiltersState, SearchResult, Tag } from "@/components/search/types";
+import { apiGet } from "@/lib/api/client";
+import type { SearchResponse } from "@/components/search/types";
+
+interface TagsResponse {
+  data: Tag[];
+}
+
+/**
+ * Knowledge search page
+ * Supports full-text search with filters for tags and status
+ */
+export default function SearchPage(): React.JSX.Element {
+  const searchParams = useSearchParams();
+  const router = useRouter();
+
+  const [query, setQuery] = useState(searchParams.get("q") ?? "");
+  const [results, setResults] = useState<SearchResult[]>([]);
+  const [totalResults, setTotalResults] = useState(0);
+  const [isLoading, setIsLoading] = useState(false);
+  const [selectedTags, setSelectedTags] = useState<string[]>([]);
+  const [selectedStatus, setSelectedStatus] = useState<string | undefined>();
+  const [availableTags, setAvailableTags] = useState<Tag[]>([]);
+
+  // Fetch available tags on mount
+  useEffect(() => {
+    const fetchTags = async (): Promise<void> => {
+      try {
+        const response = await apiGet<TagsResponse>("/api/knowledge/tags");
+        setAvailableTags(response.data);
+      } catch (error) {
+        console.error("Failed to fetch tags:", error);
+      }
+    };
+
+    void fetchTags();
+  }, []);
+
+  // Perform search when query changes
+  useEffect(() => {
+    const performSearch = async (): Promise<void> => {
+      if (!query.trim()) {
+        setResults([]);
+        setTotalResults(0);
+        return;
+      }
+
+      setIsLoading(true);
+      try {
+        // Build query params
+        const params = new URLSearchParams({ q: query });
+        if (selectedStatus) {
+          params.append("status", selectedStatus);
+        }
+        if (selectedTags.length > 0) {
+          params.append("tags", selectedTags.join(","));
+        }
+
+        const response = await apiGet<SearchResponse>(`/api/knowledge/search?${params.toString()}`);
+
+        setResults(response.data);
+        setTotalResults(response.pagination.total);
+      } catch (error) {
+        console.error("Search failed:", error);
+        setResults([]);
+        setTotalResults(0);
+      } finally {
+        setIsLoading(false);
+      }
+    };
+
+    void performSearch();
+  }, [query, selectedTags, selectedStatus]);
+
+  const handleSearch = (newQuery: string): void => {
+    setQuery(newQuery);
+    // Update URL with query
+    const params = new URLSearchParams({ q: newQuery });
+    router.push(`/knowledge/search?${params.toString()}`);
+  };
+
+  const handleFilterChange = (filters: SearchFiltersState): void => {
+    setSelectedStatus(filters.status);
+    setSelectedTags(filters.tags ?? []);
+  };
+
+  return (
+    <div className="min-h-screen bg-gray-50">
+      {/* Search header */}
+      <div className="bg-white border-b border-gray-200 p-6">
+        <div className="container mx-auto max-w-6xl">
+          <h1 className="text-3xl font-bold text-gray-900 mb-4">Search Knowledge Base</h1>
+          <SearchInput onSearch={handleSearch} initialValue={query} isLoading={isLoading} />
+        </div>
+      </div>
+
+      {/* Results area */}
+      {query && (
+        <div className="container mx-auto max-w-7xl">
+          <SearchResults
+            results={results}
+            query={query}
+            totalResults={totalResults}
+            isLoading={isLoading}
+            selectedTags={selectedTags}
+            selectedStatus={selectedStatus}
+            availableTags={availableTags}
+            onFilterChange={handleFilterChange}
+          />
+        </div>
+      )}
+
+      {/* Empty state when no query */}
+      {!query && (
+        <div className="container mx-auto max-w-6xl py-12 text-center">
+          <div className="text-6xl mb-4">🔍</div>
+          <h2 className="text-2xl font-semibold text-gray-900 mb-2">Search Your Knowledge</h2>
+          <p className="text-gray-600">
+            Enter a search term above to find entries in your knowledge base
+          </p>
+          <div className="mt-6 text-sm text-gray-500">
+            <p>Tip: Press Cmd+K (or Ctrl+K) to quickly focus the search box</p>
+          </div>
+        </div>
+      )}
+    </div>
+  );
+}