[upload] Suggest one-tap hashtag chips from the user's past videos (#45)

The upload modal's Hashtags section now shows chips of the user's most-used past
hashtags ("Reuse a tag from your videos:"). Clicking one adds it to the NIP-71 't'
repeater; already-added chips dim + disable; the row is hidden for users with no
past tags.

- js/utils/hashtagSuggestions.js: pure rankHashtagsByFrequency(videos) — count =
  number of the user's videos using each tag, normalized (case + '#') and deduped
  per video, ranked by count then alphabetically. Reads video.nip71.hashtags, falls
  back to raw event 't' tags minus bitvid's fixed t=video marker.
- app.getUserHashtagSuggestions() sources the user's own videos via
  nostrService.getActiveVideosByAuthors([pubkey]) and ranks them (top 12), injected
  into the modal as getHashtagSuggestions.
- UploadModal renders the chips on open and wires clicks through the existing
  Nip71FormManager (addRepeaterEntry + setFieldValue, dedup via collectRepeaterValues).

Tests: tests/hashtag-suggestions.test.mjs (5 — per-video counting, normalization,
marker exclusion, tie-break + limit, empty input). Lint + build green.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

js/app.js

@@ -99,6 +99,7 @@ import {
   logoutSigner,
 } from "./nostrClientRegistry.js";
 import { resolveSignerCapabilities } from "./nostr/signerCapabilities.js";
+import { rankHashtagsByFrequency } from "./utils/hashtagSuggestions.js";
 import {
   decideSignerEnsure,
   isSignerCapable,
@@ -3633,6 +3634,29 @@ class Application {
     return this._ui.updateActiveProfileUI(...args);
   }
 
+  // The active user's most-used hashtags (frequency-ranked from their own past
+  // uploads) for the upload modal's one-tap suggestion chips (TODO #45).
+  getUserHashtagSuggestions({ limit = 12 } = {}) {
+    const pubkey = this.normalizeHexPubkey(this.pubkey);
+    if (
+      !pubkey ||
+      typeof this.nostrService?.getActiveVideosByAuthors !== "function"
+    ) {
+      return [];
+    }
+    let videos = [];
+    try {
+      videos = this.nostrService.getActiveVideosByAuthors([pubkey]) || [];
+    } catch (error) {
+      devLogger.warn(
+        "[Application] Failed to read user videos for hashtag suggestions:",
+        error,
+      );
+      return [];
+    }
+    return rankHashtagsByFrequency(videos, { limit });
+  }
+
   async hydrateNwcSettingsForPubkey(pubkey) {
     return this.nwcSettingsService.hydrateNwcSettingsForPubkey(pubkey);
   }