Phase 3: JEV classification, rules table, editable categories (AUD-69)

Implements FR-3, FR-4, FR-5 and FR-14.

- internal/classify: TypeSafe System One (JEV) HTTP client with the confirmed
  request/response shape, retry with backoff on 429/529/5xx, a plain-text rule
  engine (first match wins, overrides only the named fields), and bounded
  orchestration with a per-run cap.
- internal/store: migration v3 adds an editable `categories` table (name =
  JEV Choice option and classifications key; rename cascades, remove reassigns)
  and seeds a starter rules version once. Classification persistence, coverage,
  and pending/all message queries.
- internal/server: POST /actions/classify and /actions/reclassify, plus the
  FR-14 category editor (GET /categories and add/rename/remove). The triage list
  now groups by the live category list and shows action + confidence.
- CLI: -classify and -classify-all for n8n.
- Docs: docs/phase3-classify.md with the confirmed JEV shape, a live read-only
  classification, and the DoD evidence.

DoD: all 100 stored messages have a non-null category, importance, and suggested
action (0 nulls); JEV picked a newly added/renamed category for 6 real messages
over HTTP. One live JEV call recorded in the phase doc.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

web/templates/dashboard.html

@@ -44,7 +44,10 @@
       <aside class="panel" aria-label="Categories and folders">
         <div class="nav-groups">
           <div class="nav-group">
-            <div class="nav-group-title">Categories</div>
+            <div class="nav-group-title">
+              <span>Categories</span>
+              <a class="nav-edit" href="/categories">Edit</a>
+            </div>
             <div class="nav-group-items">
               <a class="nav-item nav-item-active" href="#">
                 <span class="dot" style="background: var(--primary)"></span>
@@ -53,7 +56,7 @@
               </a>
               {{range .Categories}}
               <a class="nav-item" href="#">
-                <span class="dot" style="background: {{.Color}}"></span>
+                <span class="dot" style="background: {{.Color}}; {{if not .Count}}opacity:.35;{{end}}"></span>
                 <span>{{.Name}}</span>
                 <span class="count">{{.Count}}</span>
               </a>
@@ -84,6 +87,17 @@
                     hx-headers='{"X-CSRF-Token": "{{.CSRFToken}}"}'>
               Check mail
             </button>
+            <button class="btn btn-primary" type="button"
+                    hx-post="/actions/classify" hx-target="#inbox-list" hx-swap="innerHTML"
+                    hx-headers='{"X-CSRF-Token": "{{.CSRFToken}}"}'>
+              Classify
+            </button>
+            <button class="btn btn-utility" type="button"
+                    hx-post="/actions/reclassify" hx-target="#inbox-list" hx-swap="innerHTML"
+                    hx-confirm="Re-classify every stored message with the current categories and rules?"
+                    hx-headers='{"X-CSRF-Token": "{{.CSRFToken}}"}'>
+              Re-classify all
+            </button>
             <button class="btn btn-utility" type="button"
                     hx-get="/partials/inbox" hx-target="#inbox-list" hx-swap="innerHTML">
               Refresh