feat: add profiles, public views, settings, and code quality fixes

Phase 3 — Profiles & Public Views:
- Public profile page (/u/{username}) with OG meta tags
- User settings page (display name, bio, visibility, default privacy)
- Avatar upload with image processing
- Password change from settings (verifies current password)
- Home page shows public fave feed for logged-in users
- Must-reset-password guard redirects to /reset-password
- Profile visibility: public (full) or limited (username only)

Code quality improvements from /simplify review:
- Fix signup request persistence bug (was silently discarding data)
- Fix health check to use configured listen address, not hardcoded :8080
- Add rate limiter cleanup goroutine (was leaking memory)
- Extract shared helpers: ClearSessionCookie, IsSecureRequest, scanTags,
  scanUserFrom (scanner interface), SignupRequestStore
- Replace hand-rolled joinPlaceholders with strings.Join
- Remove dead _method hidden field, redundant devMode field
- Simplify rate-limited route registration (remove double-mux)
- Log previously-swallowed errors (session delete, image delete)
- Stop leaking internal error messages to users in image upload

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

web/templates/pages/profile.html

@@ -0,0 +1,106 @@
+{{define "head"}}
+{{with .Data}}{{with .ProfileUser}}
+    {{if eq .ProfileVisibility "public"}}
+        <meta property="og:title" content="{{.DisplayNameOrUsername}} sine favoritter">
+        <meta property="og:type" content="profile">
+        {{if $.ExternalURL}}
+            <meta property="og:url" content="{{$.ExternalURL}}/u/{{.Username}}">
+            {{if .AvatarPath}}
+                <meta property="og:image" content="{{$.ExternalURL}}/uploads/{{.AvatarPath}}">
+            {{end}}
+        {{end}}
+        <meta property="og:site_name" content="{{$.SiteName}}">
+    {{end}}
+{{end}}{{end}}
+{{end}}
+
+{{define "content"}}
+{{with .Data}}
+    {{with .ProfileUser}}
+        <section class="profile-header">
+            {{if .AvatarPath}}
+                <img src="{{basePath}}/uploads/{{.AvatarPath}}"
+                     alt="Profilbilde for {{.DisplayNameOrUsername}}"
+                     class="avatar-large">
+            {{end}}
+            <hgroup>
+                <h1>{{.DisplayNameOrUsername}}</h1>
+                {{if and (ne .DisplayName "") (ne .DisplayName .Username)}}
+                    <p>@{{.Username}}</p>
+                {{end}}
+            </hgroup>
+        </section>
+
+        {{if not $.IsLimited}}
+            {{if .Bio}}
+                <p>{{.Bio}}</p>
+            {{end}}
+
+            <p><small>Medlem siden {{.CreatedAt.Format "02.01.2006"}}</small></p>
+
+            {{if $.IsOwner}}
+                <p>
+                    <a href="{{basePath}}/settings" role="button" class="outline">Rediger profil</a>
+                    <a href="{{basePath}}/faves/new" role="button">+ Ny favoritt</a>
+                </p>
+            {{end}}
+
+            <h2>
+                {{if $.IsOwner}}Favoritter{{else}}Offentlige favoritter{{end}}
+                <small>({{$.Total}})</small>
+            </h2>
+
+            {{if $.Faves}}
+                <div class="fave-grid" role="list">
+                    {{range $.Faves}}
+                        <article class="fave-card" role="listitem">
+                            {{if .ImagePath}}
+                                <img src="{{basePath}}/uploads/{{.ImagePath}}"
+                                     alt="Bilde for: {{.Description}}"
+                                     loading="lazy">
+                            {{end}}
+                            <header>
+                                <a href="{{basePath}}/faves/{{.ID}}">
+                                    <strong>{{.Description}}</strong>
+                                </a>
+                                {{if eq .Privacy "private"}}
+                                    <small class="badge-private" aria-label="Privat">Privat</small>
+                                {{end}}
+                            </header>
+                            {{if .Tags}}
+                                <footer>
+                                    {{range .Tags}}
+                                        <a href="{{basePath}}/tags/{{.Name}}" class="tag-chip">{{.Name}}</a>
+                                    {{end}}
+                                </footer>
+                            {{end}}
+                        </article>
+                    {{end}}
+                </div>
+
+                {{if gt $.TotalPages 1}}
+                    <nav aria-label="Sidenavigasjon">
+                        <ul>
+                            {{if gt $.Page 1}}
+                                <li><a href="{{basePath}}/u/{{.Username}}?page={{subtract $.Page 1}}">← Forrige</a></li>
+                            {{end}}
+                            <li>Side {{$.Page}} av {{$.TotalPages}}</li>
+                            {{if lt $.Page $.TotalPages}}
+                                <li><a href="{{basePath}}/u/{{.Username}}?page={{add $.Page 1}}">Neste →</a></li>
+                            {{end}}
+                        </ul>
+                    </nav>
+                {{end}}
+            {{else}}
+                {{if $.IsOwner}}
+                    <p>Du har ingen favoritter ennå. <a href="{{basePath}}/faves/new">Legg til din første!</a></p>
+                {{else}}
+                    <p>Ingen offentlige favoritter ennå.</p>
+                {{end}}
+            {{end}}
+        {{else}}
+            <p><small>Denne profilen har begrenset synlighet.</small></p>
+        {{end}}
+    {{end}}
+{{end}}
+{{end}}