feat(infra): add ServerState, MongoDB, auth middleware, and DaisyUI theme toggle

Introduce centralized ServerState (Arc-wrapped, Box::leaked configs) loaded
once at startup, replacing per-request dotenvy/env::var calls across all
server functions. Add MongoDB Database wrapper with connection pooling.
Add tower middleware that gates all /api/ server function endpoints behind
session authentication (401 for unauthenticated callers, except check-auth).
Fix DaisyUI theme toggle to use certifai-dark/certifai-light theme names
and replace hardcoded hex colors in main.css with CSS variables.

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

Cargo.toml

@@ -63,7 +63,12 @@ maud = { version = "0.27", default-features = false }
 url = { version = "2.5.4", default-features = false, optional = true }
 web-sys = { version = "0.3", optional = true, features = [
     "Clipboard",
+    "Document",
+    "Element",
+    "HtmlElement",
     "Navigator",
+    "Storage",
+    "Window",
 ] }
 tracing = "0.1.40"
 # Debug
@@ -93,6 +98,8 @@ server = [
     "dep:sha2",
     "dep:base64",
     "dep:scraper",
+    "dep:secrecy",
+    "dep:petname",
 ]
 
 [[bin]]