feat: analysis providers, settings UI, song search, WAV duration fix

- Multi-provider AI analysis (Anthropic, OpenAI, Ollama, Algorithmic)
- server-only guards on all provider files; client bundle fix
- /settings page with provider status, Ollama model picker, preferences
- Song search box on /analyze replacing raw MBID input (debounced, keyboard nav)
- Auto-register song via MusicBrainz on POST /api/tracks (no more 404)
- Fix WAV duration bug: last section songEnd was double-counting elapsed time
- Registry sync comment updated for self-hosted HTTPS git servers

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/analysis/providers.ts

@@ -0,0 +1,29 @@
+import type { CTPDocument } from '@/lib/ctp/schema';
+
+export interface AnalysisInput {
+  bpm: number;
+  duration: number;       // seconds
+  title?: string;
+  artist?: string;
+  mbid?: string | null;
+  contributed_by: string;
+  ollamaModel?: string;   // required when provider id is "ollama"
+}
+
+export interface ProviderInfo {
+  id: string;
+  label: string;
+  type: 'cloud-ai' | 'local-ai' | 'algorithmic';
+  available: boolean;
+  unavailableReason?: string;   // present only when available === false
+  ollamaBaseUrl?: string;       // present only for the ollama provider
+}
+
+export interface AnalysisProvider {
+  id: string;
+  label: string;
+  type: 'cloud-ai' | 'local-ai' | 'algorithmic';
+  /** Returns true if this provider is configured and reachable. Must not throw. */
+  isAvailable(): Promise<{ available: boolean; reason?: string }>;
+  generateCTP(input: AnalysisInput): Promise<CTPDocument>;
+}