Add BCM4500 register map and fill documentation gaps

New page: bcm4500/register-map.mdx consolidates all register
addresses (direct, indirect page 0, FX2 XRAM/IRAM, I2C controller)
into a single lookup reference with cross-reference index.

Expanded sections:
- fw213-variants: hardware detection mechanism, distinguishing
  characteristics table, FW1 demod type detection signatures
- demodulator: probe logic (3x3 retry, INT0 40-iteration boot probe
  at 0x7F/0x3F, no_demod_flag graceful degradation)
- version-comparison: version ID gap aside (v2.07.04 is a kernel
  constant, not a real firmware release)

Cross-links added to signal-monitoring and tuning-protocol pages.

site/astro.config.mjs

@@ -8,6 +8,22 @@ export default defineConfig({
   devToolbar: {
     enabled: false,
   },
+  server: {
+    host: '0.0.0.0',
+    port: 4321,
+  },
+  vite: {
+    server: {
+      allowedHosts: [process.env.PUBLIC_DOMAIN, 'localhost'].filter(Boolean),
+      ...(process.env.VITE_HMR_HOST && {
+        hmr: {
+          host: process.env.VITE_HMR_HOST,
+          protocol: 'wss',
+          clientPort: 443,
+        },
+      }),
+    },
+  },
   integrations: [
     starlight({
       title: 'SkyWalker-1 Docs',
@@ -44,6 +60,7 @@ export default defineConfig({
         {
           label: 'BCM4500',
           items: [
+            { label: 'Register Map', slug: 'bcm4500/register-map' },
             { label: 'Demodulator', slug: 'bcm4500/demodulator' },
             { label: 'Tuning Protocol', slug: 'bcm4500/tuning-protocol' },
             { label: 'GPIF Streaming', slug: 'bcm4500/gpif-streaming' },
@@ -78,7 +95,8 @@ export default defineConfig({
             { label: 'Rev.2 Analysis', slug: 'firmware/rev2-analysis' },
             { label: 'Kernel FW01', slug: 'firmware/kernel-fw01' },
             { label: 'FW2.13 Variants', slug: 'firmware/fw213-variants' },
-            { label: 'Custom v3.01\u2013v3.02', slug: 'firmware/custom-v301' },
+            { label: 'Custom v3.01', slug: 'firmware/custom-v301' },
+            { label: 'Custom v3.02', slug: 'firmware/custom-v302' },
             { label: 'Storage Formats', slug: 'firmware/storage-formats' },
           ],
         },