forum: user profile pages + clickable bylines + neon pulse favicon

USER PROFILES (/forum/user/[username]):
- New API at /api/forum/user-by-username/[username] resolves by
  username OR display_name (URL-encoded), since forum threads/replies
  store author_name = display_name. Returns the persona's profile,
  thread history (up to 50), and recent replies (up to 20).
- New page renders the persona card with archetype badge
  (Audio Engineer / Colorist / etc.) + expertise level badge
  (beginner/intermediate/senior) + role title, company, location,
  years_experience, join date, and an expertise-tags chip row.
- Two columns underneath: "Threads started" and "Recent replies"
  with proper deep-links into each thread.
- Author names in /forum, /forum/[slug], and /forum/thread/[id] are
  now <Link> elements pointing to /forum/user/<displayname>, with
  onClick=stopPropagation so the card-level click handler doesn't
  also fire.

FAVICON:
- Hand-built neon pulse waveform — emerald→cyan→purple gradient on
  dark navy background, designed to read at 16×16 to 256×256.
- Multi-resolution favicon.ico (16/32/48/64) + SVG + PNGs at
  16/32/48/64/96/192/256 under /static/favicons/.
- layout.tsx icons block now references all sizes including the
  apple-touch sizes (192, 256).

No env / DB changes here — pure deploy.

src/app/forum/page.tsx

@@ -153,7 +153,7 @@ function TopThreadsWidget({ categoryId }: { categoryId?: string }) {
                   {thread.title}
                 </p>
                 <p className="text-[#555] font-body text-xs mt-0.5">
-                  <span className="text-[#666]">{thread.author_name}</span>
+                  <Link href={`/forum/user/${encodeURIComponent(thread.author_name)}`} className="text-[#666] hover:text-[#3b82f6] hover:underline" onClick={(e) => e.stopPropagation()}>{thread.author_name}</Link>
                   {thread.forum_categories && (
                     <> · <span className="text-[#3b82f6]">{thread.forum_categories.name}</span></>
                   )}
@@ -483,7 +483,7 @@ export default function ForumIndexPage() {
                               {thread.title}
                             </h3>
                             <p className="text-[#666] font-body text-xs mt-0.5">
-                              by <span className="text-[#888]">{thread.author_name}</span>
+                              by <Link href={`/forum/user/${encodeURIComponent(thread.author_name)}`} className="text-[#888] hover:text-[#3b82f6] hover:underline" onClick={(e) => e.stopPropagation()}>{thread.author_name}</Link>
                               {thread.forum_categories && (
                                 <> · <span className="text-[#3b82f6]">{thread.forum_categories.name}</span></>
                               )}