Implement payments system with default free allowance and quota enforcement (#17)

* Initial plan for issue

* Implement complete payments system with quota enforcement

- Add default free allowance configuration (100MB)
- Implement quota checking before uploads in both blossom and nip96 routes
- Add comprehensive quota checking functions in database module
- Enhance admin API to show quota information
- Add payment processing infrastructure
- Include all necessary database migrations

Users now get 100MB free storage + any valid paid storage.
Uploads are rejected when quota would be exceeded.

* Move free_quota_bytes to PaymentConfig and restore mime_type parameter

Co-authored-by: v0l <1172179+v0l@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: v0l <1172179+v0l@users.noreply.github.com>

src/routes/blossom.rs

@@ -25,7 +25,7 @@ pub struct BlobDescriptor {
     pub size: u64,
     #[serde(rename = "type", skip_serializing_if = "Option::is_none")]
     pub mime_type: Option<String>,
-    pub uploaded: u64,
+    pub created: u64,
     #[serde(rename = "nip94", skip_serializing_if = "Option::is_none")]
     pub nip94: Option<HashMap<String, String>>,
 }
@@ -45,7 +45,7 @@ impl BlobDescriptor {
             sha256: id_hex,
             size: value.size,
             mime_type: Some(value.mime_type.clone()),
-            uploaded: value.created.timestamp() as u64,
+            created: value.created.timestamp() as u64,
             nip94: Some(
                 Nip94Event::from_upload(settings, value)
                     .tags
@@ -362,6 +362,21 @@ async fn process_upload(
         return e;
     }
 
+    // check quota
+    #[cfg(feature = "payments")]
+    if let Some(upload_size) = size {
+        let free_quota = settings.payments.as_ref()
+            .and_then(|p| p.free_quota_bytes)
+            .unwrap_or(104857600); // Default to 100MB
+        let pubkey_vec = auth.event.pubkey.to_bytes().to_vec();
+        
+        match db.check_user_quota(&pubkey_vec, upload_size, free_quota).await {
+            Ok(false) => return BlossomResponse::error("Upload would exceed quota"),
+            Err(_) => return BlossomResponse::error("Failed to check quota"),
+            Ok(true) => {} // Quota check passed
+        }
+    }
+
     process_stream(
         data.open(ByteUnit::Byte(settings.max_upload_bytes)),
         &auth
@@ -415,7 +430,7 @@ where
             return BlossomResponse::error(format!("Failed to save file (db): {}", e));
         }
     };
-    if let Err(e) = db.add_file(&upload, Some(user_id)).await {
+    if let Err(e) = db.add_file(&upload, user_id).await {
         error!("{}", e.to_string());
         BlossomResponse::error(format!("Error saving file (db): {}", e))
     } else {