feat(suggestions): user-managed blocklist for noisy auto-tags

Adds a tag_suggestion_blocklist table + service-layer filter so the
user can permanently suppress specific canonical tag names from the
suggestion stream (WD14 anatomy/composition tags like '1girl',
'breasts', 'nipples' that aren't useful for the discoverability use
case this app targets).

Data model
  - migration k26042201: tag_suggestion_blocklist(name TEXT PK, created_at)
  - model TagSuggestionBlocklistEntry

Service
  - tag_suggestions._blocklisted_names() snapshots the current set
  - get_suggestions filters merged results before grouping, so both
    WD14- and embedding-sourced suggestions respect the blocklist
  - get_bulk_suggestions inherits the filter via its per-image call
    to get_suggestions

API
  - GET  /api/suggestions/blocklist           -> {ok, names}
  - POST /api/suggestions/blocklist           -> add one
  - POST /api/suggestions/blocklist/delete    -> remove one
  - POST /api/suggestions/blocklist/bulk      -> replace the whole list
    (backs the settings textarea save button)

UI
  - modal suggestion chip gets a third action button (⊘) alongside
    accept (✓) / reject (✕). Clicking it adds the name to the
    blocklist, logs a rejection for ML feedback on this image, and
    sweeps every chip on the page carrying that same name.
  - Settings -> Maintenance -> Suggestion blocklist section with a
    monospaced textarea (one name per line) + Save. Loads current
    entries on mount.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/models.py

@@ -310,3 +310,16 @@ class TagSuggestionConfig(db.Model):
     key = db.Column(db.Text, primary_key=True)
     value = db.Column(db.Text, nullable=False)
     description = db.Column(db.Text, nullable=True)
+
+
+class TagSuggestionBlocklistEntry(db.Model):
+    """Canonical tag names the user never wants surfaced as a suggestion.
+
+    Matched by exact string against the canonicalized WD14 name (post
+    underscores-to-space + title-case for character/fandom). Filter applies
+    in app.services.tag_suggestions.get_suggestions, after WD14 + embedding
+    results are merged and before they're grouped for the client.
+    """
+    __tablename__ = "tag_suggestion_blocklist"
+    name = db.Column(db.Text, primary_key=True)
+    created_at = db.Column(db.DateTime(timezone=True), server_default=db.func.now(), nullable=False)