Add author detail, idea detail, and gap-draft reverse link pages

- Author detail page (/authors/<person_id>): shows author info, all drafts
  with ratings, and co-authors with shared draft counts. Public route.
- Idea detail page (/ideas/<idea_id>): shows idea metadata, source draft,
  and top-5 most similar ideas via embedding cosine similarity. Admin route.
- Gap detail page: added "Related Drafts" section that finds drafts by
  extracting draft names from evidence text and searching by topic keywords.
- Updated author links across templates to use /authors/<person_id> URLs.
- Added DB methods: get_author_by_id, get_author_drafts, get_coauthors.
- Extended top_authors to include person_id (5th tuple element).

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

src/ietf_analyzer/db.py

@@ -639,10 +639,10 @@ class Database:
     def author_count(self) -> int:
         return self.conn.execute("SELECT COUNT(*) FROM authors").fetchone()[0]
 
-    def top_authors(self, limit: int = 20) -> list[tuple[str, str, int, list[str]]]:
-        """Return (name, affiliation, draft_count, [draft_names])."""
+    def top_authors(self, limit: int = 20) -> list[tuple[str, str, int, list[str], int]]:
+        """Return (name, affiliation, draft_count, [draft_names], person_id)."""
         rows = self.conn.execute(
-            """SELECT a.name, a.affiliation, COUNT(da.draft_name) as cnt,
+            """SELECT a.person_id, a.name, a.affiliation, COUNT(da.draft_name) as cnt,
                 GROUP_CONCAT(da.draft_name, '||') as drafts
             FROM authors a
             JOIN draft_authors da ON a.person_id = da.person_id
@@ -653,10 +653,50 @@ class Database:
         ).fetchall()
         return [
             (r["name"], r["affiliation"], r["cnt"],
-             r["drafts"].split("||") if r["drafts"] else [])
+             r["drafts"].split("||") if r["drafts"] else [],
+             r["person_id"])
             for r in rows
         ]
 
+    def get_author_by_id(self, person_id: int) -> dict | None:
+        """Return author info by person_id, or None if not found."""
+        row = self.conn.execute(
+            "SELECT * FROM authors WHERE person_id = ?", (person_id,)
+        ).fetchone()
+        if not row:
+            return None
+        return {
+            "person_id": row["person_id"],
+            "name": row["name"],
+            "ascii_name": row["ascii_name"],
+            "affiliation": row["affiliation"],
+            "resource_uri": row["resource_uri"],
+        }
+
+    def get_author_drafts(self, person_id: int) -> list[str]:
+        """Return draft names for a given author."""
+        rows = self.conn.execute(
+            "SELECT draft_name FROM draft_authors WHERE person_id = ? ORDER BY draft_name",
+            (person_id,),
+        ).fetchall()
+        return [r["draft_name"] for r in rows]
+
+    def get_coauthors(self, person_id: int) -> list[dict]:
+        """Return co-authors for a given person (authors on the same drafts)."""
+        rows = self.conn.execute(
+            """SELECT DISTINCT a.person_id, a.name, a.affiliation, COUNT(DISTINCT da2.draft_name) as shared
+            FROM draft_authors da1
+            JOIN draft_authors da2 ON da1.draft_name = da2.draft_name AND da2.person_id != da1.person_id
+            JOIN authors a ON da2.person_id = a.person_id
+            WHERE da1.person_id = ?
+            GROUP BY a.person_id
+            ORDER BY shared DESC""",
+            (person_id,),
+        ).fetchall()
+        return [{"person_id": r["person_id"], "name": r["name"],
+                 "affiliation": r["affiliation"], "shared_drafts": r["shared"]}
+                for r in rows]
+
     def top_orgs(self, limit: int = 20) -> list[tuple[str, int, int]]:
         """Return (org, author_count, draft_count)."""
         rows = self.conn.execute(