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/openai.ts

@@ -0,0 +1,108 @@
+import 'server-only';
+
+import type { CTPDocument } from "@/lib/ctp/schema";
+import type { AnalysisInput, AnalysisProvider } from "@/lib/analysis/providers";
+import { CTP_SCHEMA, SYSTEM_PROMPT } from "./anthropic";
+
+function buildLabel(): string {
+  const model = process.env.OPENAI_MODEL ?? "GPT-4o";
+  const baseUrl = process.env.OPENAI_BASE_URL ?? "";
+  if (baseUrl && !baseUrl.includes("api.openai.com")) {
+    try {
+      const host = new URL(baseUrl).hostname;
+      return `${model} (${host})`;
+    } catch {
+      // fall through
+    }
+  }
+  return `${model} (OpenAI)`;
+}
+
+export const openaiProvider: AnalysisProvider = {
+  id: "openai",
+  label: buildLabel(),
+  type: "cloud-ai",
+
+  async isAvailable() {
+    if (process.env.OPENAI_API_KEY) {
+      return { available: true };
+    }
+    return { available: false, reason: "OPENAI_API_KEY not set" };
+  },
+
+  async generateCTP(input: AnalysisInput): Promise<CTPDocument> {
+    const apiKey = process.env.OPENAI_API_KEY;
+    if (!apiKey) {
+      throw new Error("OPENAI_API_KEY not set");
+    }
+
+    const baseUrl = process.env.OPENAI_BASE_URL ?? "https://api.openai.com/v1";
+    const model = process.env.OPENAI_MODEL ?? "gpt-4o";
+    const { bpm, duration, title, artist, mbid, contributed_by } = input;
+    const approxBars = Math.round((duration * bpm) / 60 / 4);
+
+    const userMessage = `\
+Generate a CTP document for the following song:
+
+Title: ${title ?? "Unknown Title"}
+Artist: ${artist ?? "Unknown Artist"}
+MusicBrainz ID: ${mbid ?? "unknown"}
+Detected BPM: ${bpm}
+Duration: ${duration.toFixed(1)} seconds (~${approxBars} bars at 4/4)
+Contributed by: ${contributed_by}
+
+Create a plausible section layout for this song. If this is a well-known song, use your knowledge of its actual arrangement. If not, use a sensible generic structure.`;
+
+    const response = await fetch(`${baseUrl}/chat/completions`, {
+      method: "POST",
+      headers: {
+        "Content-Type": "application/json",
+        Authorization: `Bearer ${apiKey}`,
+      },
+      body: JSON.stringify({
+        model,
+        messages: [
+          { role: "system", content: SYSTEM_PROMPT },
+          { role: "user", content: userMessage },
+        ],
+        response_format: {
+          type: "json_schema",
+          json_schema: {
+            strict: true,
+            name: "CTPDocument",
+            schema: CTP_SCHEMA,
+          },
+        },
+        max_tokens: 2048,
+      }),
+    });
+
+    if (!response.ok) {
+      const text = await response.text().catch(() => "");
+      throw new Error(`OpenAI API error ${response.status}: ${text.slice(0, 200)}`);
+    }
+
+    const json = await response.json() as {
+      choices?: Array<{ message?: { content?: string } }>;
+    };
+
+    const content = json.choices?.[0]?.message?.content;
+    if (!content) {
+      throw new Error("OpenAI did not return a message content");
+    }
+
+    let parsed: unknown;
+    try {
+      parsed = JSON.parse(content);
+    } catch {
+      throw new Error(`OpenAI returned invalid JSON: ${content.slice(0, 200)}`);
+    }
+
+    const doc = parsed as CTPDocument;
+    if (!doc.metadata.created_at || doc.metadata.created_at.includes("placeholder")) {
+      doc.metadata.created_at = new Date().toISOString();
+    }
+
+    return doc;
+  },
+};