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/registry.ts

@@ -0,0 +1,78 @@
+import 'server-only';
+
+import type { AnalysisProvider, ProviderInfo } from "@/lib/analysis/providers";
+import { anthropicProvider } from "./anthropic";
+import { openaiProvider } from "./openai";
+import { ollamaProvider, getOllamaModels } from "./ollama";
+import { algorithmicProvider } from "./algorithmic";
+import { RECOMMENDED_OLLAMA_MODELS } from "@/lib/analysis/constants";
+
+export { getOllamaModels, RECOMMENDED_OLLAMA_MODELS };
+
+// Registration order determines the default when the user has no saved preference.
+const ALL_PROVIDERS: AnalysisProvider[] = [
+  anthropicProvider,
+  openaiProvider,
+  ollamaProvider,
+  algorithmicProvider,
+];
+
+/**
+ * Returns every provider with its current availability status.
+ * Runs all isAvailable() checks in parallel.
+ */
+export async function getProviderInfoList(): Promise<ProviderInfo[]> {
+  const results = await Promise.all(
+    ALL_PROVIDERS.map(async (p) => {
+      const availability = await p.isAvailable();
+      const info: ProviderInfo = {
+        id: p.id,
+        label: p.label,
+        type: p.type,
+        available: availability.available,
+      };
+      if (!availability.available && availability.reason) {
+        info.unavailableReason = availability.reason;
+      }
+      if (p.id === "ollama") {
+        info.ollamaBaseUrl = process.env.OLLAMA_BASE_URL ?? "http://localhost:11434";
+      }
+      return info;
+    })
+  );
+  return results;
+}
+
+/**
+ * Returns only providers where available === true.
+ * The algorithmic provider is always included.
+ */
+export async function getAvailableProviders(): Promise<AnalysisProvider[]> {
+  const checks = await Promise.all(
+    ALL_PROVIDERS.map(async (p) => {
+      const availability = await p.isAvailable();
+      return { provider: p, available: availability.available };
+    })
+  );
+  return checks.filter((c) => c.available).map((c) => c.provider);
+}
+
+/**
+ * Looks up a provider by id. Throws with a descriptive message if not found
+ * or if isAvailable() returns false.
+ */
+export async function getProvider(id: string): Promise<AnalysisProvider> {
+  const provider = ALL_PROVIDERS.find((p) => p.id === id);
+  if (!provider) {
+    throw new Error(
+      `Unknown provider '${id}'. Available providers: ${ALL_PROVIDERS.map((p) => p.id).join(", ")}`
+    );
+  }
+  const availability = await provider.isAvailable();
+  if (!availability.available) {
+    throw new Error(
+      `Provider '${id}' is not available: ${availability.reason ?? "unknown reason"}`
+    );
+  }
+  return provider;
+}