[CRCR] Add nightly tab to CI summary page (#8377)

## Summary

Adds event-type tabs (**Pull Requests** | **Nightly**) to the CRCR CI
summary page (`hud.pytorch.org/crcr`), enabling visibility into nightly
CI results from downstream repos alongside existing PR CI data.

### Changes

- **New ClickHouse query `crcr_nightly_summary`**: Aggregates nightly CI
results per downstream repo, filtering on `event_type = 'nightly'`,
including the latest tested SHA
- **Filter PR data**: Adds `AND pr_number > 0` to `crcr_summary` query
to prevent nightly rows from appearing in the PR tab
- **Nightly tab UI**: Tab-based navigation with repo count badges, a
nightly results table with SHA links, and an empty state when no nightly
data exists yet

### Dependencies

- Depends on #8353 for the `event_type` column in `crcr_workflow_job`
ClickHouse schema

### Mockup

**Design**:
https://subinz1.github.io/CRCR/mockups/crcr-summary-nightly-design.html

### Test plan

- [ ] Verify PR tab displays current CRCR data as before
- [ ] Verify Nightly tab shows empty state (no nightly data reported
yet)
- [ ] Once #8353 is deployed, verify nightly results appear in the
Nightly tab
- [ ] Verify tab count badges update correctly
- [ ] Verify SHA links point to correct pytorch/pytorch commits

Author: subinz1

torchci/clickhouse_queries/crcr_nightly_summary/params.json

@@ -0,0 +1,10 @@
+{
+  "params": {
+    "days": "UInt64"
+  },
+  "tests": [
+    {
+      "days": "7"
+    }
+  ]
+}

torchci/clickhouse_queries/crcr_nightly_summary/query.sql

@@ -0,0 +1,21 @@
+SELECT
+    downstream_repo AS repo,
+    anyLast(downstream_repo_level) AS downstream_repo_level,
+    countIf(conclusion = 'success') AS successes,
+    countIf(conclusion = 'failure') AS failures,
+    countIf(conclusion = 'timed_out') AS timed_out,
+    count() AS total,
+    if(total > 0, successes / total, 0) AS pass_rate,
+    avg(duration_seconds) AS avg_duration_s,
+    max(started_at) AS last_run,
+    argMax(pytorch_head_sha, started_at) AS latest_sha
+FROM
+    default.crcr_workflow_job FINAL
+WHERE
+    started_at > now() - INTERVAL {days: UInt64} DAY
+    AND status = 'completed'
+    AND event_type = 'nightly'
+GROUP BY
+    repo
+ORDER BY
+    pass_rate ASC