fix: replace silent error swallowing with console.warn and user-facing error messages

All empty catch blocks across 8 Vue pages now log warnings. User-initiated
actions (fight, matchmake) also surface errors in the UI via fightError/loadError refs.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/pages/FightPage.vue

@@ -192,7 +192,9 @@ async function loadFight(): Promise<string | null> {
       }
       return data.status
     }
-  } catch { /* */ }
+  } catch (err) {
+    console.warn('[FightPage] loadFight failed:', err)
+  }
   return null
 }
 
@@ -254,7 +256,9 @@ async function pollForChallenge() {
     } else if (humanSubmitted.value) {
       humanChallenge.value = null
     }
-  } catch { /* */ }
+  } catch (err) {
+    console.warn('[FightPage] pollForChallenge failed:', err)
+  }
 }
 
 function startTimer() {
@@ -287,7 +291,9 @@ async function submitHumanAnswer() {
       headers: { 'Content-Type': 'application/json' },
       body: JSON.stringify({ answer: humanAnswer.value.trim() }),
     })
-  } catch { /* */ }
+  } catch (err) {
+    console.warn('[FightPage] submitHumanAnswer failed:', err)
+  }
 }
 
 // --- Live scene management ---
@@ -350,7 +356,9 @@ function connectSSE() {
         color: 'neon-green',
       })
       scrollLiveLog()
-    } catch { /* */ }
+    } catch (err) {
+      console.warn('[FightPage] SSE round_start parse failed:', err)
+    }
   })
 
   eventSource.addEventListener('human_challenge', async (e) => {
@@ -377,19 +385,25 @@ function connectSSE() {
       } else {
         applyChallenge(sseData)
       }
-    } catch { /* */ }
+    } catch (err) {
+      console.warn('[FightPage] SSE human_challenge failed:', err)
+    }
   })
 
   eventSource.addEventListener('round_end', (e) => {
     try {
       handleRoundEnd(JSON.parse(e.data))
-    } catch { /* */ }
+    } catch (err) {
+      console.warn('[FightPage] SSE round_end failed:', err)
+    }
   })
 
   eventSource.addEventListener('fight_end', (e) => {
     try {
       handleFightEnd(JSON.parse(e.data))
-    } catch { /* */ }
+    } catch (err) {
+      console.warn('[FightPage] SSE fight_end failed:', err)
+    }
   })
 
   let sseRetries = 0
@@ -492,7 +506,9 @@ async function handleRoundEnd(data: any) {
         botAScore: result.botAScore || 0,
         botBScore: result.botBScore || 0,
       })
-    } catch { /* */ }
+    } catch (err) {
+      console.warn('[FightPage] playRound animation failed:', err)
+    }
 
     if (aWon || bWon) {
       await liveScene.playTaunt(aWon ? 'a' : 'b')
@@ -679,8 +695,13 @@ async function fightAgain(botId: string) {
         await nextTick()
         if (liveFightData.value) await initLiveScene()
       }
+    } else {
+      fightError.value = `Failed to start fight (${res.status})`
     }
-  } catch { /* */ }
+  } catch (err) {
+    fightError.value = 'Network error starting fight'
+    console.warn('[FightPage] fightAgain failed:', err)
+  }
   isRequeueing.value = false
 }
 
@@ -699,8 +720,13 @@ async function matchmake(botId: string) {
       fightError.value = ''
       window.history.replaceState({}, '', `/arena/${data.fightId}`)
       startPolling()
+    } else {
+      fightError.value = `Matchmaking failed (${res.status})`
     }
-  } catch { /* */ }
+  } catch (err) {
+    fightError.value = 'Network error during matchmaking'
+    console.warn('[FightPage] matchmake failed:', err)
+  }
   isRequeueing.value = false
 }