fix: keep the public screens usable on an empty site, and centre the dialogs

The published site showed one line of text — "요청한 문구를 표시할 수 없습니다."
— instead of any UI. Two independent faults produced it.

The screens ask for the whole catalogue by calling searchPublicContent(""). The
fixture answered that with everything it had, and four screens lean on it: the
home timeline, the project index, the release index, and the explore filter.
The contract has no such meaning — `q` is required, and an empty one answers
400 — so all four turned into error surfaces the moment the source became HTTP.
The adapter now assembles that catalogue from the list endpoints the contract
does provide, and only sends a real query to the search endpoint. Filtering
client-side instead would have been the other option, and it would silently
lose every result past the first page.

The message that surfaced was missing too. Twenty-two of the thirty-eight
failure kinds had no copy, so `errorMessage` fell through to
`common.unavailable` — which says nothing about what failed or what to do.
That is a systemic gap, not one absent key, so all twenty-two are written, in
both catalogues. They are phrased for the reader: what did not happen and what
to try, not the internal classification.

The Studio dialogs opened against the top-left corner. A modal dialog centres
through the UA's `margin: auto`, which is not surviving in this build; the
public `.search-dialog` already states `position/inset/margin` explicitly for
the same reason. The three that did not — unsaved-changes, asset upload, and
the publication flow — now follow it, with a max-height so a long dialog
scrolls rather than running off the screen.

src/features/tech-log/presentation/styles/studio.css

@@ -30,7 +30,11 @@
 .studio-app .studio-route-state button { min-height: 44px; margin-top: 18px; padding-inline: 16px; border: 1px solid var(--signal); border-radius: 5px; background: var(--signal); color: #fff; }
 .studio-app .studio-loading { min-height: 180px; }
 .studio-app .studio-visually-hidden { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0, 0, 0, 0); white-space: nowrap; border: 0; }
-.studio-app .studio-unsaved-dialog { width: min(560px, calc(100% - 32px)); padding: 0; border: 1px solid var(--line-strong); border-radius: 8px; background: var(--paper); color: var(--ink); }
+/* 모달 dialog 를 화면 가운데에 둔다. UA 기본값(margin:auto)에 맡기면 이 빌드에서는
+   좌상단에 붙는다 — 공개 화면의 .search-dialog 가 같은 이유로 position/inset/margin 을
+   이미 명시하고 있고, 여기도 같은 방식을 쓴다. max-height/overflow 는 내용이 길어졌을 때
+   화면 밖으로 나가지 않게 하는 짝이다. */
+.studio-app .studio-unsaved-dialog { position: fixed; inset: 0; margin: auto; max-height: calc(100dvh - 32px); overflow: auto; width: min(560px, calc(100% - 32px)); padding: 0; border: 1px solid var(--line-strong); border-radius: 8px; background: var(--paper); color: var(--ink); }
 .studio-app .studio-unsaved-dialog::backdrop { background: rgba(23, 24, 27, 0.48); }
 .studio-app .studio-dialog-body { padding: 30px; }
 .studio-app .studio-dialog-body h2 { margin: 0 0 12px; font-size: 26px; }
@@ -38,7 +42,7 @@
 .studio-app .studio-dialog-actions { display: flex; flex-wrap: wrap; justify-content: flex-end; gap: 8px; margin-top: 28px; }
 .studio-app .studio-dialog-actions button { min-height: 44px; padding-inline: 14px; border: 1px solid var(--line-strong); border-radius: 5px; background: var(--paper); color: var(--ink); }
 .studio-app .studio-dialog-actions button:last-child { border-color: var(--signal); background: var(--signal); color: #fff; }
-.studio-app .studio-asset-upload-dialog { width: min(560px, calc(100% - 32px)); padding: 0; border: 1px solid var(--line-strong); border-radius: 8px; background: var(--paper); color: var(--ink); }
+.studio-app .studio-asset-upload-dialog { position: fixed; inset: 0; margin: auto; max-height: calc(100dvh - 32px); overflow: auto; width: min(560px, calc(100% - 32px)); padding: 0; border: 1px solid var(--line-strong); border-radius: 8px; background: var(--paper); color: var(--ink); }
 .studio-app .studio-asset-upload-dialog::backdrop { background: rgba(23, 24, 27, 0.48); }
 .studio-app .studio-asset-upload-dialog .studio-dialog-status { min-height: 20px; margin: 16px 0 0; color: var(--muted); font-size: 13px; }
 .studio-app .studio-asset-upload-dialog .studio-field + .studio-field { margin-top: 18px; }