fix: cleanup docs issues

- Remove duplicate fee-sponsorship.mdx (orphaned page not in sidebar)
  - Add 301 redirect to canonical /guide/payments/sponsor-user-fees
- Remove _template.mdx to fix 'Replace Me' appearing in search
- Fix broken #payments-lane anchor links in tip20 pages
  - Correct anchor is #get-predictable-payment-fees

Amp-Thread-ID: https://ampcode.com/threads/T-019be114-04be-71cb-9110-401d83b5e771
Co-authored-by: Amp <amp@ampcode.com>

Author: gakonst

src/pages/guide/_template.mdx

@@ -25,7 +25,7 @@ Below are some of the key benefits and features of TIP-20 tokens:
   />
   <Card
     description="TIP-20 tokens have dedicated blockspace from all other transactions, ensuring predictable payment fees."
-    to="#payments-lane"
+    to="#get-predictable-payment-fees"
     icon="lucide:route"
     title="Get Predictable Payment Fees"
   />

src/pages/guide/use-accounts/fee-sponsorship.mdx

@@ -23,7 +23,7 @@ Below are some of the key benefits and features of TIP-20 tokens:
   />
   <Card
     description="TIP-20 tokens have dedicated blockspace from all other transactions, ensuring predictable payment fees."
-    to="#payments-lane"
+    to="#get-predictable-payment-fees"
     icon="lucide:route"
     title="Get Predictable Payment Fees"
   />

src/pages/protocol/tip20/overview.mdx

@@ -672,6 +672,11 @@ export default defineConfig({
       source: '/sdk/typescript/prool',
       destination: '/sdk/typescript/prool/setup',
     },
+    {
+      source: '/guide/use-accounts/fee-sponsorship',
+      destination: '/guide/payments/sponsor-user-fees',
+      status: 301,
+    },
   ],
   twoslash: {
     twoslashOptions: {