Replace Handlebars with flexible template engine system

- Replace handlebars dependency with optional liquidjs and mustache
- Add templateEngine string configuration ('liquidjs', 'mustache', 'simple')
- Add custom templateRenderer hook for maximum flexibility
- Implement graceful fallbacks when optional dependencies unavailable
- Fix webpack compatibility issues with require.extensions
- Maintain backward compatibility with existing templates
- Add comprehensive template syntax documentation

🤖 Generated with [Claude Code](https://claude.ai/code)

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

pnpm-lock.yaml

@@ -8,9 +8,9 @@ importers:
 
   .:
     dependencies:
-      handlebars:
-        specifier: ^4.7.8
-        version: 4.7.8
+      liquidjs:
+        specifier: ^10.19.0
+        version: 10.21.1
       nodemailer:
         specifier: ^6.9.8
         version: 6.10.1
@@ -2637,6 +2637,10 @@ packages:
   colorette@2.0.20:
     resolution: {integrity: sha512-IfEDxwoWIjkeXL1eXcDiow4UbKjhLdq6/EuSVR9GMN7KVH3r9gQ83e73hsz1Nd1T3ijd5xv1wcWRYO+D6kCI2w==}
 
+  commander@10.0.1:
+    resolution: {integrity: sha512-y4Mg2tXshplEbSGzx7amzPwKKOCGuoSRP/CjEdwwk0FOGlUbq6lKuoyDZTNZkmxHdJtp54hdfY/JUrdL7Xfdug==}
+    engines: {node: '>=14'}
+
   commander@2.20.3:
     resolution: {integrity: sha512-GpVkmM8vF2vQUkj2LvZmD35JxeJOLCwJ9cUkugyk2nuhbv3+mJvpLYYt+0+USMxE+oj+ey/lJEnhZw75x/OMcQ==}
 
@@ -3540,11 +3544,6 @@ packages:
     resolution: {integrity: sha512-mS1lbMsxgQj6hge1XZ6p7GPhbrtFwUFYi3wRzXAC/FmYnyXMTvvI3td3rjmQ2u8ewXueaSvRPWaEcgVVOT9Jnw==}
     engines: {node: ^12.22.0 || ^14.16.0 || ^16.0.0 || >=17.0.0}
 
-  handlebars@4.7.8:
-    resolution: {integrity: sha512-vafaFqs8MZkRrSX7sFVUdo3ap/eNiLnb4IakshzvP56X5Nr1iGKAIqdX6tMlm6HcNRIkr6AxO5jFEoJzzpT8aQ==}
-    engines: {node: '>=0.4.7'}
-    hasBin: true
-
   has-bigints@1.1.0:
     resolution: {integrity: sha512-R3pbpkcIqv2Pm3dUwgjclDRVmWpTJW2DcMzcIhEXEx1oh/CEMObMm3KLmRJOdvhM7o4uQBnwr8pzRK2sJWIqfg==}
     engines: {node: '>= 0.4'}
@@ -3922,6 +3921,11 @@ packages:
   lines-and-columns@1.2.4:
     resolution: {integrity: sha512-7ylylesZQ/PV29jhEDl3Ufjo6ZX7gCqJr5F7PKrqc93v7fzSymt1BpwEU8nAUXs8qzzvqhbjhK5QZg6Mt/HkBg==}
 
+  liquidjs@10.21.1:
+    resolution: {integrity: sha512-NZXmCwv3RG5nire3fmIn9HsOyJX3vo+ptp0yaXUHAMzSNBhx74Hm+dAGJvscUA6lNqbLuYfXgNavRQ9UbUJhQQ==}
+    engines: {node: '>=14'}
+    hasBin: true
+
   locate-path@5.0.0:
     resolution: {integrity: sha512-t7hw9pI+WvuwNJXwk5zVHpyhIqzg2qTlklJOf0mVxGSbe3Fp2VieZcduNYjaLDoy6p9uGpQEGWG87WpMKlNq8g==}
     engines: {node: '>=8'}
@@ -4202,9 +4206,6 @@ packages:
   natural-compare@1.4.0:
     resolution: {integrity: sha512-OWND8ei3VtNC9h7V60qff3SVobHr996CTwgxubgyQYEpg290h9J0buyECNNJexkFm5sOajh5G116RYA1c8ZMSw==}
 
-  neo-async@2.6.2:
-    resolution: {integrity: sha512-Yd3UES5mWCSqR+qNT93S3UoYUkqAZ9lLg8a7g9rimsWmYGK8cVToA4/sF3RrshdyV3sAGMXVUmpMYOw+dLpOuw==}
-
   new-find-package-json@2.0.0:
     resolution: {integrity: sha512-lDcBsjBSMlj3LXH2v/FW3txlh2pYTjmbOXPYJD93HI5EwuLzI11tdHSIpUMmfq/IOsldj4Ps8M8flhm+pCK4Ew==}
     engines: {node: '>=12.22.0'}
@@ -5170,11 +5171,6 @@ packages:
     engines: {node: '>=14.17'}
     hasBin: true
 
-  uglify-js@3.19.3:
-    resolution: {integrity: sha512-v3Xu+yuwBXisp6QYTcH4UbH+xYJXqnq2m/LtQVWKWzYc1iehYnLixoQDN9FH6/j9/oybfd6W9Ghwkl8+UMKTKQ==}
-    engines: {node: '>=0.8.0'}
-    hasBin: true
-
   uint8array-extras@1.5.0:
     resolution: {integrity: sha512-rvKSBiC5zqCCiDZ9kAOszZcDvdAHwwIKJG33Ykj43OKcWsnmcBRL09YTU4nOeHZ8Y2a7l1MgTd08SBe9A8Qj6A==}
     engines: {node: '>=18'}
@@ -5377,9 +5373,6 @@ packages:
     resolution: {integrity: sha512-BN22B5eaMMI9UMtjrGd5g5eCYPpCPDUy0FJXbYsaT5zYxjFOckS53SQDE3pWkVoWpHXVb3BrYcEN4Twa55B5cA==}
     engines: {node: '>=0.10.0'}
 
-  wordwrap@1.0.0:
-    resolution: {integrity: sha512-gvVzJFlPycKc5dZN4yPkP8w7Dc37BtP1yczEneOb4uq34pXZcvrtRTmWV8W+Ume+XCxKgbjM+nevkyFPMybd4Q==}
-
   wrap-ansi@7.0.0:
     resolution: {integrity: sha512-YVGIj2kamLSTxw6NsZjoBxfSwsn0ycdesmc4p+Q21c5zPuZ1pl+NfxVdxPtdHvmNVOQ6XSYG4AUtyt/Fi7D16Q==}
     engines: {node: '>=10'}
@@ -8540,6 +8533,8 @@ snapshots:
 
   colorette@2.0.20: {}
 
+  commander@10.0.1: {}
+
   commander@2.20.3: {}
 
   commander@6.2.1: {}
@@ -9689,15 +9684,6 @@ snapshots:
 
   graphql@16.11.0: {}
 
-  handlebars@4.7.8:
-    dependencies:
-      minimist: 1.2.8
-      neo-async: 2.6.2
-      source-map: 0.6.1
-      wordwrap: 1.0.0
-    optionalDependencies:
-      uglify-js: 3.19.3
-
   has-bigints@1.1.0: {}
 
   has-flag@4.0.0: {}
@@ -10044,6 +10030,10 @@ snapshots:
 
   lines-and-columns@1.2.4: {}
 
+  liquidjs@10.21.1:
+    dependencies:
+      commander: 10.0.1
+
   locate-path@5.0.0:
     dependencies:
       p-locate: 4.1.0
@@ -10439,8 +10429,6 @@ snapshots:
 
   natural-compare@1.4.0: {}
 
-  neo-async@2.6.2: {}
-
   new-find-package-json@2.0.0:
     dependencies:
       debug: 4.4.1
@@ -11571,9 +11559,6 @@ snapshots:
 
   typescript@5.9.2: {}
 
-  uglify-js@3.19.3:
-    optional: true
-
   uint8array-extras@1.5.0: {}
 
   unbox-primitive@1.1.0:
@@ -11820,8 +11805,6 @@ snapshots:
 
   word-wrap@1.2.5: {}
 
-  wordwrap@1.0.0: {}
-
   wrap-ansi@7.0.0:
     dependencies:
       ansi-styles: 4.3.0