feat: add model picker to Analysis and Batch pages with full backend wiring

Thread the optional model parameter through the entire analysis pipeline:
- analyzer.py: analyze_company, _analyze_company_safe, analyze_companies,
  and analyze_single_patent now accept and forward model override
- api.py: single company endpoint accepts model query param; batch and
  async batch endpoints pass request.model through to the analyzer
- client.ts: analyzeCompany, analyzeBatch, analyzeBatchAsync accept model;
  add listModels() to fetch available models from GET /models
- Analysis.tsx: add model selector dropdown that loads from /models API
- Batch.tsx: add model selector alongside the workers slider

Users can now pick a specific LLM (GPT-4o, Claude 3.5, Gemini, etc.)
per analysis request, or leave it on the server default.

Closes leeworks-agents/SPARC#351

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/api/client.ts

@@ -89,29 +89,53 @@ export const authApi = {
   },
 };
 
+// Model types
+export interface ModelInfo {
+  id: string;
+  name: string;
+  provider: string;
+}
+
+export interface ModelsResponse {
+  models: ModelInfo[];
+  default: string;
+}
+
 // Analysis API
 export const analysisApi = {
-  analyzeCompany: async (companyName: string): Promise<CompanyAnalysis> => {
-    const response = await api.get<CompanyAnalysis>(`/analyze/${encodeURIComponent(companyName)}`);
+  analyzeCompany: async (companyName: string, model?: string): Promise<CompanyAnalysis> => {
+    const params = new URLSearchParams();
+    if (model) params.append('model', model);
+    const qs = params.toString();
+    const response = await api.get<CompanyAnalysis>(
+      `/analyze/${encodeURIComponent(companyName)}${qs ? `?${qs}` : ''}`
+    );
     return response.data;
   },
 
-  analyzeBatch: async (companies: string[], maxWorkers = 3): Promise<BatchAnalysisResult> => {
+  analyzeBatch: async (companies: string[], maxWorkers = 3, model?: string): Promise<BatchAnalysisResult> => {
     const response = await api.post<BatchAnalysisResult>('/analyze/batch', {
       companies,
       max_workers: maxWorkers,
+      ...(model ? { model } : {}),
     });
     return response.data;
   },
 
-  analyzeBatchAsync: async (companies: string[], maxWorkers = 3): Promise<JobStatus> => {
+  analyzeBatchAsync: async (companies: string[], maxWorkers = 3, model?: string): Promise<JobStatus> => {
     const response = await api.post<JobStatus>('/analyze/batch/async', {
       companies,
       max_workers: maxWorkers,
+      ...(model ? { model } : {}),
     });
     return response.data;
   },
 
+  listModels: async (): Promise<ModelsResponse> => {
+    const response = await api.get<ModelsResponse>('/models');
+    return response.data;
+  },
+
   getJobStatus: async (jobId: string): Promise<JobStatus> => {
     const response = await api.get<JobStatus>(`/jobs/${jobId}`);
     return response.data;