feat: add DaisyUI v5 theming, PKCE auth, and Keycloak realm export

- Add DaisyUI v5 with custom certifai-dark/certifai-light themes using oklch colors
- Create styles/input.css as Tailwind + DaisyUI entry point (replaces root tailwind.css)
- Add SVG brand logo combining shield motif with neural network nodes
- Implement PKCE (S256) for OAuth authorization code flow
- Add Keycloak realm-export.json with test users for local development
- Fix CSS load order in app.rs (tailwind before main.css) and add data-theme attribute

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

Cargo.toml

@@ -73,6 +73,8 @@ dioxus-free-icons = { version = "0.10", features = [
     "bootstrap",
     "font-awesome-solid",
 ] }
+sha2 = { version = "0.10.9", default-features = false, optional = true }
+base64 = { version = "0.22.1", default-features = false, optional = true }
 
 [features]
 # default = ["web"]
@@ -87,6 +89,8 @@ server = [
     "dep:time",
     "dep:rand",
     "dep:url",
+    "dep:sha2",
+    "dep:base64",
 ]
 
 [[bin]]