Add volume mapping docs and build/version metadata

Add a volume-mapping guide and surface build/version metadata throughout the project.

Changes included:
- documentation: Add documentation/deployment/volume-mapping.md and update TABLEOFCONTENTS.md and README to reference it (helps users align download client and RMAB paths).
- CI: Capture package.json version in .github/workflows/build-unified-image.yml, pass APP_VERSION as a build-arg, and update the Discord notification to show the semantic version and pull `:latest`.
- Docker: Declare ARG APP_VERSION and expose NEXT_PUBLIC_APP_VERSION / APP_VERSION / GIT_COMMIT env vars in dockerfile.unified so runtime and client can read the semantic version and commit.
- App API/UI: Update src/app/api/version/route.ts and src/components/ui/VersionBadge.tsx to prefer semantic app version (APP_VERSION / NEXT_PUBLIC_APP_VERSION), include fullVersion and commit info, show commit in tooltip, and adjust fallback/dev labels.
- Tests: Update tests (system.routes.test.ts and VersionBadge.test.tsx) to reflect the new version/commit fields and behavior.
- Audible integration: Add ipRedirectOverride query param to multiple Audible requests to avoid IP-based region redirects.
- Misc: Bump package.json version to 1.0.0.

These changes make version information consistent between build, runtime, and UI, improve CI notifications, add user guidance for common volume-mapping issues, and harden Audible scraping against region redirects.

tests/api/system.routes.test.ts

@@ -57,16 +57,17 @@ describe('System routes', () => {
   });
 
   it('returns version info from environment', async () => {
-    process.env.APP_VERSION = 'abcdef123456';
+    process.env.APP_VERSION = '1.0.0';
+    process.env.GIT_COMMIT = 'abcdef123456';
     process.env.BUILD_DATE = '2025-01-01';
 
     const { GET } = await import('@/app/api/version/route');
     const response = await GET();
     const payload = await response.json();
 
-    expect(payload.shortCommit).toBe('abcdef1');
+    expect(payload.version).toBe('v1.0.0');
+    expect(payload.fullVersion).toBe('1.0.0');
+    expect(payload.commit).toBe('abcdef123456');
     expect(payload.buildDate).toBe('2025-01-01');
   });
 });
-
-