feat: add shares service layer with batch fetch and hydration

Create shares-service.ts with fetchSharesForNotes, createShare,
revokeShare, getShareByNoteId, and getSharedNote. Integrate share
tokens into hydrateNotes pipeline alongside tags, attachments,
and collaborators.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pnpm-lock.yaml

@@ -80,6 +80,9 @@ importers:
       markdown-it:
         specifier: ^14.1.1
         version: 14.1.1
+      nanoid:
+        specifier: ^5.1.7
+        version: 5.1.7
       node-diff3:
         specifier: ^3.2.0
         version: 3.2.0
@@ -2998,6 +3001,11 @@ packages:
     engines: {node: ^10 || ^12 || ^13.7 || ^14 || >=15.0.1}
     hasBin: true
 
+  nanoid@5.1.7:
+    resolution: {integrity: sha512-ua3NDgISf6jdwezAheMOk4mbE1LXjm1DfMUDMuJf4AqxLFK3ccGpgWizwa5YV7Yz9EpXwEaWoRXSb/BnV0t5dQ==}
+    engines: {node: ^18 || >=20}
+    hasBin: true
+
   napi-build-utils@2.0.0:
     resolution: {integrity: sha512-GEbrYkbfF7MoNaoh2iGG84Mnf/WZfB0GdGEsM8wz7Expx/LlWf5U8t9nvJKXSp3qr5IsEbK04cBGhol/KwOsWA==}
 
@@ -6783,6 +6791,8 @@ snapshots:
 
   nanoid@3.3.11: {}
 
+  nanoid@5.1.7: {}
+
   napi-build-utils@2.0.0: {}
 
   negotiator@1.0.0: {}