Add per-instance mod management with client-side detection

- New mod validation engine (src/mods.rs) with constant-pool class-file
  scanning: detects server-side content (block, tileentity, command,
  worldgen) vs client-only API (gui, renderer, forge/client)
- 7 client-only mods correctly detected (AppleSkin, CraftingTweaks,
  Durability101, EnchantmentDescriptions, InventoryHUD, MouseTweaks,
  TrashSlot); 51 server-capable; 1 unknown
- Routes + templating for mod upload (jar/zip), listing, delete, rescan
- Multipart upload with 500MB limit (bypasses axum's default 2MB)
- Per-instance mod summary card on edit page
- Whitelist toggle checkbox on edit page (persisted, drives ENABLE_WHITELIST)
- Dynamic Java image tag (java8/java17/java21) based on MC version
- Class scan is informational-only; rejection based on metadata side=CLIENT
- has_modpack flag cleanup on mod delete
- Remove hx-boost from <body> (was corrupting multipart uploads)

1 files changed, 2 insertions, 0 deletions

diff --git a/src/routes/mod.rs b/src/routes/mod.rs
index 1cb0e54..a4d200c 100644
--- a/src/routes/mod.rs
+++ b/src/routes/mod.rs
@@ -2,6 +2,7 @@ pub mod accounts;
 pub mod backups;
 pub mod dashboard;
 pub mod instances;
+pub mod mods;
 pub mod players;
 
 use askama::Template;
@@ -35,6 +36,7 @@ pub fn build_router(state: AppState) -> Router {
         .merge(players::router())
         .merge(accounts::router())
         .merge(backups::router())
+        .merge(mods::router())
         .layer(auth_required);
 
     Router::new()