fix(ingestion): label upsert reliability, init idempotency, and sync health

Label upsert (issues + merge_requests): Replace INSERT ... ON CONFLICT DO
UPDATE RETURNING with INSERT OR IGNORE + SELECT. The prior RETURNING-based
approach relied on last_insert_rowid() matching the returned id, which is
not guaranteed when ON CONFLICT triggers an update (SQLite may return 0).
The new two-step approach is unambiguous and correctly tracks created_count.

Init: Add ON CONFLICT(gitlab_project_id) DO UPDATE to the project insert
so re-running `lore init` updates path/branch/url instead of failing with
a unique constraint violation.

MR discussions sync: Reset discussions_sync_attempts to 0 when clearing a
sync health error, so previously-failed MRs get a fresh retry budget after
successful sync.

Count: format_number now handles negative numbers correctly by extracting
the sign before inserting thousand-separators.

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

src/cli/commands/count.rs

@@ -179,9 +179,15 @@ fn count_notes(conn: &Connection, type_filter: Option<&str>) -> Result<CountResu
 }
 
 fn format_number(n: i64) -> String {
-    let s = n.to_string();
+    let (prefix, abs) = if n < 0 {
+        ("-", n.unsigned_abs())
+    } else {
+        ("", n.unsigned_abs())
+    };
+
+    let s = abs.to_string();
     let chars: Vec<char> = s.chars().collect();
-    let mut result = String::new();
+    let mut result = String::from(prefix);
 
     for (i, c) in chars.iter().enumerate() {
         if i > 0 && (chars.len() - i).is_multiple_of(3) {