chore: community feedback fixes and UI improvements (#102)

## Summary

Addresses all community feedback tickets from the last deploy, plus several UI improvements made during the same session.

### Bug fixes & balance
- **#97** — Fix auto-adventurer tier priority: sort by combat power instead of current cost so the highest-tier affordable unit is always purchased
- **#98** — Add Dark Templar adventurer (80k CP) to bridge the Volcanic Depths progression wall; rewire upgrade and quest rewards accordingly
- **#99** — Reorder and buff Shadow Assassin (55k CP, level 12) so Witch Coven feels rewarding rather than a regression
- **#100** — Display effective Gold/s (all multipliers applied) in the resource bar
- **#101** — Add Peasant tier 2 (10x, essence) and tier 3 (50x, crystals) upgrades for meaningful late-game scaling

### Other fixes
- Sync game state to server before auto-boss challenges (matching manual challenge behaviour)
- Refresh Discord avatar hash on every game load via bot token so stale CDN URLs are corrected automatically

### UI improvements
- Replace Donate / Discord / Support / View Profile / Edit Profile buttons with a single avatar dropdown menu
- Collapse all resources except Gold into a click-to-toggle dropdown; orange alert dot appears when a hidden resource is capped

## Closes

Closes #97
Closes #98
Closes #99
Closes #100
Closes #101

Reviewed-on: #102
Co-authored-by: Hikari <hikari@nhcarrigan.com>
Co-committed-by: Hikari <hikari@nhcarrigan.com>

apps/api/test/services/discord.spec.ts

@@ -104,4 +104,53 @@ describe("discord service", () => {
       await expect(exchangeCode("some_code")).rejects.toBe("raw string error");
     });
   });
+
+  describe("fetchDiscordUserById", () => {
+    it("returns null when DISCORD_BOT_TOKEN is missing", async () => {
+      delete process.env["DISCORD_BOT_TOKEN"];
+      const { fetchDiscordUserById } = await import("../../src/services/discord.js");
+      const result = await fetchDiscordUserById("123456");
+      expect(result).toBeNull();
+    });
+
+    it("returns null when DISCORD_BOT_TOKEN is empty", async () => {
+      process.env["DISCORD_BOT_TOKEN"] = "";
+      const { fetchDiscordUserById } = await import("../../src/services/discord.js");
+      const result = await fetchDiscordUserById("123456");
+      expect(result).toBeNull();
+    });
+
+    it("returns null when response is not ok", async () => {
+      process.env["DISCORD_BOT_TOKEN"] = "bot_token";
+      mockFetch.mockResolvedValueOnce({ ok: false, statusText: "Not Found" });
+      const { fetchDiscordUserById } = await import("../../src/services/discord.js");
+      const result = await fetchDiscordUserById("123456");
+      expect(result).toBeNull();
+    });
+
+    it("returns null when fetch throws", async () => {
+      process.env["DISCORD_BOT_TOKEN"] = "bot_token";
+      mockFetch.mockRejectedValueOnce(new Error("network error"));
+      const { fetchDiscordUserById } = await import("../../src/services/discord.js");
+      const result = await fetchDiscordUserById("123456");
+      expect(result).toBeNull();
+    });
+
+    it("returns null when fetch throws a non-Error value", async () => {
+      process.env["DISCORD_BOT_TOKEN"] = "bot_token";
+      mockFetch.mockRejectedValueOnce("raw string error");
+      const { fetchDiscordUserById } = await import("../../src/services/discord.js");
+      const result = await fetchDiscordUserById("123456");
+      expect(result).toBeNull();
+    });
+
+    it("returns the user on success", async () => {
+      process.env["DISCORD_BOT_TOKEN"] = "bot_token";
+      const user = { id: "123456", username: "testuser", discriminator: "0", avatar: "abc123" };
+      mockFetch.mockResolvedValueOnce({ ok: true, json: () => Promise.resolve(user) });
+      const { fetchDiscordUserById } = await import("../../src/services/discord.js");
+      const result = await fetchDiscordUserById("123456");
+      expect(result).toMatchObject({ id: "123456", avatar: "abc123" });
+    });
+  });
 });