test: comprehensive test coverage expansion (+965 tests)

Add 42 new test files covering all untested tool routes, image engine
internals, AI sidecar bridge, Zustand stores, and cross-format
compatibility. Expand e2e-docker suite with 7 spec files covering all
48 tools against a real Docker container.

Unit tests:
- Image engine: format detection, MIME mapping, metadata parsing, pipeline
- AI bridge: sidecar lifecycle, all 11 tool functions (mocked)
- Web stores: 14 Zustand stores (collage, settings, features, analytics, etc.)
- API helpers: format decoders, page range, file validation

Integration tests:
- 25 tool routes that had zero dedicated tests
- Cross-format matrix: 17 input formats x 3 tools
- Edge cases: zero-byte files, corrupted headers, path traversal, XSS, SQL injection
- Concurrent request handling and pipeline edge cases

E2E-Docker (Playwright against real container):
- 7 spec files: essential, adjustment, conversion, creative, utility, AI, pipeline
- Custom buildMultipart helper for multi-file tool uploads
- AI tools gracefully skip when sidecar not installed

Fixtures:
- Organized test media: formats/ (18 formats) + content/ (17 content types)
- Reduced from 3.1 GB unorganized samples to 33 MB structured fixtures

Bug fix:
- color-adjustments: gamma exposure used invalid single-param gamma() for
  positive values; fixed to use two-param gamma(gammaIn, gammaOut) form

tests/integration/image-to-base64.test.ts

@@ -0,0 +1,196 @@
+/**
+ * Integration tests for the image-to-base64 tool.
+ *
+ * Converts image(s) to base64 strings. Custom route that returns JSON
+ * with results/errors arrays rather than a file download.
+ */
+
+import { readFileSync } from "node:fs";
+import { join } from "node:path";
+import { afterAll, beforeAll, describe, expect, it } from "vitest";
+import { buildTestApp, createMultipartPayload, loginAsAdmin, type TestApp } from "./test-server.js";
+
+const FIXTURES = join(__dirname, "..", "fixtures");
+const PNG = readFileSync(join(FIXTURES, "test-200x150.png"));
+const JPG = readFileSync(join(FIXTURES, "test-100x100.jpg"));
+
+let testApp: TestApp;
+let app: TestApp["app"];
+let adminToken: string;
+
+beforeAll(async () => {
+  testApp = await buildTestApp();
+  app = testApp.app;
+  adminToken = await loginAsAdmin(app);
+}, 30_000);
+
+afterAll(async () => {
+  await testApp.cleanup();
+}, 10_000);
+
+describe("image-to-base64", () => {
+  it("converts a PNG to base64", async () => {
+    const { body, contentType } = createMultipartPayload([
+      { name: "file", filename: "test.png", contentType: "image/png", content: PNG },
+      { name: "settings", content: JSON.stringify({}) },
+    ]);
+
+    const res = await app.inject({
+      method: "POST",
+      url: "/api/v1/tools/image-to-base64",
+      headers: { authorization: `Bearer ${adminToken}`, "content-type": contentType },
+      body,
+    });
+
+    expect(res.statusCode).toBe(200);
+    const json = JSON.parse(res.body);
+    expect(json.results).toHaveLength(1);
+    expect(json.errors).toHaveLength(0);
+
+    const result = json.results[0];
+    expect(result.filename).toBe("test.png");
+    expect(result.base64).toBeDefined();
+    expect(result.base64.length).toBeGreaterThan(0);
+    expect(result.dataUri).toMatch(/^data:image\/.+;base64,/);
+    expect(result.mimeType).toContain("image/");
+    expect(result.width).toBeGreaterThan(0);
+    expect(result.height).toBeGreaterThan(0);
+    expect(result.originalSize).toBe(PNG.length);
+    expect(result.encodedSize).toBeGreaterThan(0);
+    expect(typeof result.overheadPercent).toBe("number");
+  });
+
+  it("base64 output is valid", async () => {
+    const { body, contentType } = createMultipartPayload([
+      { name: "file", filename: "test.png", contentType: "image/png", content: PNG },
+      { name: "settings", content: JSON.stringify({}) },
+    ]);
+
+    const res = await app.inject({
+      method: "POST",
+      url: "/api/v1/tools/image-to-base64",
+      headers: { authorization: `Bearer ${adminToken}`, "content-type": contentType },
+      body,
+    });
+
+    expect(res.statusCode).toBe(200);
+    const json = JSON.parse(res.body);
+    const b64 = json.results[0].base64;
+    // Verify it decodes without error
+    const decoded = Buffer.from(b64, "base64");
+    expect(decoded.length).toBeGreaterThan(0);
+    // Re-encoding should match
+    expect(decoded.toString("base64")).toBe(b64);
+  });
+
+  it("converts multiple images", async () => {
+    const { body, contentType } = createMultipartPayload([
+      { name: "file", filename: "img1.png", contentType: "image/png", content: PNG },
+      { name: "file", filename: "img2.jpg", contentType: "image/jpeg", content: JPG },
+      { name: "settings", content: JSON.stringify({}) },
+    ]);
+
+    const res = await app.inject({
+      method: "POST",
+      url: "/api/v1/tools/image-to-base64",
+      headers: { authorization: `Bearer ${adminToken}`, "content-type": contentType },
+      body,
+    });
+
+    expect(res.statusCode).toBe(200);
+    const json = JSON.parse(res.body);
+    expect(json.results).toHaveLength(2);
+    expect(json.results[0].filename).toBe("img1.png");
+    expect(json.results[1].filename).toBe("img2.jpg");
+  });
+
+  it("converts to a specific output format", async () => {
+    const { body, contentType } = createMultipartPayload([
+      { name: "file", filename: "test.png", contentType: "image/png", content: PNG },
+      { name: "settings", content: JSON.stringify({ outputFormat: "jpeg" }) },
+    ]);
+
+    const res = await app.inject({
+      method: "POST",
+      url: "/api/v1/tools/image-to-base64",
+      headers: { authorization: `Bearer ${adminToken}`, "content-type": contentType },
+      body,
+    });
+
+    expect(res.statusCode).toBe(200);
+    const json = JSON.parse(res.body);
+    expect(json.results[0].mimeType).toBe("image/jpeg");
+    expect(json.results[0].dataUri).toMatch(/^data:image\/jpeg;base64,/);
+  });
+
+  it("applies maxWidth resize", async () => {
+    const { body, contentType } = createMultipartPayload([
+      { name: "file", filename: "test.png", contentType: "image/png", content: PNG },
+      { name: "settings", content: JSON.stringify({ maxWidth: 50 }) },
+    ]);
+
+    const res = await app.inject({
+      method: "POST",
+      url: "/api/v1/tools/image-to-base64",
+      headers: { authorization: `Bearer ${adminToken}`, "content-type": contentType },
+      body,
+    });
+
+    expect(res.statusCode).toBe(200);
+    const json = JSON.parse(res.body);
+    expect(json.results[0].width).toBeLessThanOrEqual(50);
+  });
+
+  it("applies maxHeight resize", async () => {
+    const { body, contentType } = createMultipartPayload([
+      { name: "file", filename: "test.png", contentType: "image/png", content: PNG },
+      { name: "settings", content: JSON.stringify({ maxHeight: 50 }) },
+    ]);
+
+    const res = await app.inject({
+      method: "POST",
+      url: "/api/v1/tools/image-to-base64",
+      headers: { authorization: `Bearer ${adminToken}`, "content-type": contentType },
+      body,
+    });
+
+    expect(res.statusCode).toBe(200);
+    const json = JSON.parse(res.body);
+    expect(json.results[0].height).toBeLessThanOrEqual(50);
+  });
+
+  it("rejects request without any files", async () => {
+    const { body, contentType } = createMultipartPayload([
+      { name: "settings", content: JSON.stringify({}) },
+    ]);
+
+    const res = await app.inject({
+      method: "POST",
+      url: "/api/v1/tools/image-to-base64",
+      headers: { authorization: `Bearer ${adminToken}`, "content-type": contentType },
+      body,
+    });
+
+    expect(res.statusCode).toBe(400);
+    const json = JSON.parse(res.body);
+    expect(json.error).toContain("No image files");
+  });
+
+  it("rejects invalid quality setting", async () => {
+    const { body, contentType } = createMultipartPayload([
+      { name: "file", filename: "test.png", contentType: "image/png", content: PNG },
+      { name: "settings", content: JSON.stringify({ quality: 0 }) },
+    ]);
+
+    const res = await app.inject({
+      method: "POST",
+      url: "/api/v1/tools/image-to-base64",
+      headers: { authorization: `Bearer ${adminToken}`, "content-type": contentType },
+      body,
+    });
+
+    expect(res.statusCode).toBe(400);
+    const json = JSON.parse(res.body);
+    expect(json.error).toContain("Invalid settings");
+  });
+});