feat(auth): add user registration endpoint

Implement POST /api/auth/register endpoint with:
- Argon2 password hashing
- Zod validation for username (1-255 chars) and password (8-255 chars)
- Duplicate username check (returns 409 Conflict)
- Returns created user with id, username, and createdAt

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

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

1 files changed, 94 insertions, 0 deletions

diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index 4f13349..9ce2ee0 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -22,6 +22,12 @@ importers:
       '@hono/node-server':
         specifier: ^1.19.6
         version: 1.19.6(hono@4.10.7)
+      '@kioku/shared':
+        specifier: workspace:*
+        version: link:../shared
+      argon2:
+        specifier: ^0.44.0
+        version: 0.44.0
       drizzle-orm:
         specifier: ^0.44.7
         version: 0.44.7(@types/pg@8.15.6)(pg@8.16.3)
@@ -109,6 +115,9 @@ packages:
   '@drizzle-team/brocli@0.10.2':
     resolution: {integrity: sha512-z33Il7l5dKjUgGULTqBsQBQwckHh5AbIuxhdsIxDDiZAzBOrZO6q9ogcWC65kU382AfynTfgNumVcNIjuIua6w==}
 
+  '@epic-web/invariant@1.0.0':
+    resolution: {integrity: sha512-lrTPqgvfFQtR/eY/qkIzp98OGdNJu0m5ji3q/nJI8v3SXkRKEnWiOxMmbvcSoAIzv/cGiuvRy57k4suKQSAdwA==}
+
   '@esbuild-kit/core-utils@3.3.2':
     resolution: {integrity: sha512-sPRAnw9CdSsRmEtnsl2WXWdyquogVpB3yZ3dgwJfe8zrOzTsV7cJvmwrKVa+0ma5BoiGJ+BoqkMvawbayKUsqQ==}
     deprecated: 'Merged into tsx: https://tsx.is'
@@ -414,6 +423,10 @@ packages:
   '@jridgewell/sourcemap-codec@1.5.5':
     resolution: {integrity: sha512-cYQ9310grqxueWbl+WuIUIaiUaDcj7WOq5fVhEljNVgRfOUhY9fy2zTvfoqWsnebh8Sl70VScFbICvJnLKB0Og==}
 
+  '@phc/format@1.0.0':
+    resolution: {integrity: sha512-m7X9U6BG2+J+R1lSOdCiITLLrxm+cWlNI3HUFA92oLO77ObGNzaKdh8pMLqdZcshtkKuV84olNNXDfMc4FezBQ==}
+    engines: {node: '>=10'}
+
   '@rollup/rollup-android-arm-eabi@4.53.3':
     resolution: {integrity: sha512-mRSi+4cBjrRLoaal2PnqH82Wqyb+d3HsPUN/W+WslCXsZsyHa9ZeQQX/pQsZaVIWDkPcpV6jJ+3KLbTbgnwv8w==}
     cpu: [arm]
@@ -571,6 +584,10 @@ packages:
   '@vitest/utils@4.0.14':
     resolution: {integrity: sha512-hLqXZKAWNg8pI+SQXyXxWCTOpA3MvsqcbVeNgSi8x/CSN2wi26dSzn1wrOhmCmFjEvN9p8/kLFRHa6PI8jHazw==}
 
+  argon2@0.44.0:
+    resolution: {integrity: sha512-zHPGN3S55sihSQo0dBbK0A5qpi2R31z7HZDZnry3ifOyj8bZZnpZND2gpmhnRGO1V/d555RwBqIK5W4Mrmv3ig==}
+    engines: {node: '>=16.17.0'}
+
   assertion-error@2.0.1:
     resolution: {integrity: sha512-Izi8RQcffqCeNVgFigKli1ssklIbpHnCYc6AknXGYoB6grJqyeby7jv12JUQgmTAnIDnbck1uxksT4dzN3PWBA==}
     engines: {node: '>=12'}
@@ -582,6 +599,15 @@ packages:
     resolution: {integrity: sha512-p4Z49OGG5W/WBCPSS/dH3jQ73kD6tiMmUM+bckNK6Jr5JHMG3k9bg/BvKR8lKmtVBKmOiuVaV2ws8s9oSbwysg==}
     engines: {node: '>=18'}
 
+  cross-env@10.1.0:
+    resolution: {integrity: sha512-GsYosgnACZTADcmEyJctkJIoqAhHjttw7RsFrVoJNXbsWWqaq6Ym+7kZjq6mS45O0jij6vtiReppKQEtqWy6Dw==}
+    engines: {node: '>=20'}
+    hasBin: true
+
+  cross-spawn@7.0.6:
+    resolution: {integrity: sha512-uV2QOWP2nWzsy2aMp8aRibhi9dlzF5Hgh5SHaB9OiTGEyDTiJJyx0uy51QXdyWbtAHNua4XJzUKca3OzKUd3vA==}
+    engines: {node: '>= 8'}
+
   debug@4.4.3:
     resolution: {integrity: sha512-RGwwWnwQvkVfavKVt22FGLw+xYSdzARwm0ru6DhTVA3umU5hZc28V3kO4stgYryrTlLpuvgI9GiijltAjNbcqA==}
     engines: {node: '>=6.0'}
@@ -733,6 +759,9 @@ packages:
     resolution: {integrity: sha512-icXIITfw/07Q88nLSkB9aiUrd8rYzSweK681Kjo/TSggaGbOX4RRyxxm71v+3PC8C/j+4rlxGeoTRxQDkaJkUw==}
     engines: {node: '>=16.9.0'}
 
+  isexe@2.0.0:
+    resolution: {integrity: sha512-RHxMLp9lnKHGHRng9QFhRCMbYAcVpn69smSGcq3f36xjgVVWThj4qqLbTLlq7Ssj8B+fIQ1EuCEGI2lKsyQeIw==}
+
   magic-string@0.30.21:
     resolution: {integrity: sha512-vd2F4YUyEXKGcLHoq+TEyCjxueSeHnFxyyjNp80yg0XV4vUhnDer/lvvlqM/arB5bXQN5K2/3oinyCRyx8T2CQ==}
 
@@ -744,9 +773,21 @@ packages:
     engines: {node: ^10 || ^12 || ^13.7 || ^14 || >=15.0.1}
     hasBin: true
 
+  node-addon-api@8.5.0:
+    resolution: {integrity: sha512-/bRZty2mXUIFY/xU5HLvveNHlswNJej+RnxBjOMkidWfwZzgTbPG1E3K5TOxRLOR+5hX7bSofy8yf1hZevMS8A==}
+    engines: {node: ^18 || ^20 || >= 21}
+
+  node-gyp-build@4.8.4:
+    resolution: {integrity: sha512-LA4ZjwlnUblHVgq0oBF3Jl/6h/Nvs5fzBLwdEF4nuxnFdsfajde4WfxtJr3CaiH+F6ewcIB/q4jQ4UzPyid+CQ==}
+    hasBin: true
+
   obug@2.1.1:
     resolution: {integrity: sha512-uTqF9MuPraAQ+IsnPf366RG4cP9RtUi7MLO1N3KEc+wb0a6yKpeL0lmk2IB1jY5KHPAlTc6T/JRdC/YqxHNwkQ==}
 
+  path-key@3.1.1:
+    resolution: {integrity: sha512-ojmeN0qd+y0jszEtoY48r0Peq5dwMEkIlCOu6Q5f41lfkswXuKtYrhgoTpLnyIcHm24Uhqx+5Tqm2InSwLhE6Q==}
+    engines: {node: '>=8'}
+
   pathe@2.0.3:
     resolution: {integrity: sha512-WUjGcAqP1gQacoQe+OBJsFA7Ld4DyXuUIjZ5cc75cLHvJ7dtNsTugphxIADwspS+AraAUePCKrSVtPLFj/F88w==}
 
@@ -819,6 +860,14 @@ packages:
     engines: {node: '>=18.0.0', npm: '>=8.0.0'}
     hasBin: true
 
+  shebang-command@2.0.0:
+    resolution: {integrity: sha512-kHxr2zZpYtdmrN1qDjrrX/Z1rR1kG8Dx+gkpK1G4eXmvXswmcE1hTWBWYUzlraYw1/yZp6YuDY77YtvbN0dmDA==}
+    engines: {node: '>=8'}
+
+  shebang-regex@3.0.0:
+    resolution: {integrity: sha512-7++dFhtcx3353uBaq8DDR4NuxBetBzC7ZQOhmTQInHEd6bSrXdiEyzCvG07Z44UYdLShWUyXt5M/yhz8ekcb1A==}
+    engines: {node: '>=8'}
+
   siginfo@2.0.0:
     resolution: {integrity: sha512-ybx0WO1/8bSBLEWXZvEd7gMW3Sn3JFlW3TvX1nREbDLRNQNaeNN8WK0meBwPdAaOI7TtRRRJn/Es1zhrrCHu7g==}
 
@@ -939,6 +988,11 @@ packages:
       jsdom:
         optional: true
 
+  which@2.0.2:
+    resolution: {integrity: sha512-BLI3Tl1TW3Pvl70l3yq3Y64i+awpwXqsGBYWkkqMtnbXgrMD+yj7rhW0kuEDxzJaYXGjEW5ogapKNMEKNMjibA==}
+    engines: {node: '>= 8'}
+    hasBin: true
+
   why-is-node-running@2.3.0:
     resolution: {integrity: sha512-hUrmaWBdVDcxvYqnyh09zunKzROWjbZTiNy8dBEjkS7ehEDQibXJ7XvlmtbwuTclUiIyN+CyXQD4Vmko8fNm8w==}
     engines: {node: '>=8'}
@@ -990,6 +1044,8 @@ snapshots:
 
   '@drizzle-team/brocli@0.10.2': {}
 
+  '@epic-web/invariant@1.0.0': {}
+
   '@esbuild-kit/core-utils@3.3.2':
     dependencies:
       esbuild: 0.18.20
@@ -1150,6 +1206,8 @@ snapshots:
 
   '@jridgewell/sourcemap-codec@1.5.5': {}
 
+  '@phc/format@1.0.0': {}
+
   '@rollup/rollup-android-arm-eabi@4.53.3':
     optional: true
 
@@ -1276,12 +1334,30 @@ snapshots:
       '@vitest/pretty-format': 4.0.14
       tinyrainbow: 3.0.3
 
+  argon2@0.44.0:
+    dependencies:
+      '@phc/format': 1.0.0
+      cross-env: 10.1.0
+      node-addon-api: 8.5.0
+      node-gyp-build: 4.8.4
+
   assertion-error@2.0.1: {}
 
   buffer-from@1.1.2: {}
 
   chai@6.2.1: {}
 
+  cross-env@10.1.0:
+    dependencies:
+      '@epic-web/invariant': 1.0.0
+      cross-spawn: 7.0.6
+
+  cross-spawn@7.0.6:
+    dependencies:
+      path-key: 3.1.1
+      shebang-command: 2.0.0
+      which: 2.0.2
+
   debug@4.4.3:
     dependencies:
       ms: 2.1.3
@@ -1382,6 +1458,8 @@ snapshots:
 
   hono@4.10.7: {}
 
+  isexe@2.0.0: {}
+
   magic-string@0.30.21:
     dependencies:
       '@jridgewell/sourcemap-codec': 1.5.5
@@ -1390,8 +1468,14 @@ snapshots:
 
   nanoid@3.3.11: {}
 
+  node-addon-api@8.5.0: {}
+
+  node-gyp-build@4.8.4: {}
+
   obug@2.1.1: {}
 
+  path-key@3.1.1: {}
+
   pathe@2.0.3: {}
 
   pg-cloudflare@1.2.7:
@@ -1479,6 +1563,12 @@ snapshots:
       '@rollup/rollup-win32-x64-msvc': 4.53.3
       fsevents: 2.3.3
 
+  shebang-command@2.0.0:
+    dependencies:
+      shebang-regex: 3.0.0
+
+  shebang-regex@3.0.0: {}
+
   siginfo@2.0.0: {}
 
   source-map-js@1.2.1: {}
@@ -1560,6 +1650,10 @@ snapshots:
       - tsx
       - yaml
 
+  which@2.0.2:
+    dependencies:
+      isexe: 2.0.0
+
   why-is-node-running@2.3.0:
     dependencies:
       siginfo: 2.0.0