feat(i18n): add French language support and enhance localization

- Introduced French as a supported language across the application, updating locale files and adding translations for various components.
- Enhanced language handling logic to accommodate French, ensuring proper detection and fallback mechanisms.
- Updated UI elements to include French language options, improving accessibility for French-speaking users.
- Refactored SEO handling to include French in hreflang links, enhancing search engine indexing for multilingual content.
- Added new scripts for managing French translations and ensuring consistency across language files.

frontend/src/views/falukant/PoliticsView.vue

@@ -149,7 +149,7 @@
                                 :value="e.id"
                                 :disabled="e.alreadyApplied || e.canApplyByAge === false"
                             />
-                            <span>Für diese Kandidatur vormerken</span>
+                            <span>{{ $t('falukant.politics.bookmarkCandidate') }}</span>
                         </label>
                     </article>
                 </div>
@@ -552,10 +552,10 @@ export default {
                     { votes: singlePayload }
                 );
                 await this.loadElections();
-                showSuccess(this, 'Stimme erfolgreich abgegeben.');
+                showSuccess(this, this.$t('falukant.politics.voteSuccess'));
             } catch (err) {
                 console.error(`Error submitting vote for election ${electionId}`, err);
-                showApiError(this, err, 'Fehler beim Abgeben der Stimme');
+                showApiError(this, err, this.$t('falukant.politics.voteError'));
             }
         },
 
@@ -573,10 +573,10 @@ export default {
                     { votes: payload }
                 );
                 await this.loadElections();
-                showSuccess(this, 'Alle Stimmen erfolgreich abgegeben.');
+                showSuccess(this, this.$t('falukant.politics.voteAllSuccess'));
             } catch (err) {
                 console.error('Error submitting all votes', err);
-                showApiError(this, err, 'Fehler beim Abgeben der Stimmen');
+                showApiError(this, err, this.$t('falukant.politics.voteAllError'));
             }
         },
 
@@ -632,7 +632,7 @@ export default {
                 this.selectedApplications = this.openPolitics
                     .filter(e => e.alreadyApplied || appliedIds.includes(e.id))
                     .map(e => e.id);
-                showSuccess(this, 'Kandidatur erfolgreich vorgemerkt.');
+                showSuccess(this, this.$t('falukant.politics.applyBookmarkSuccess'));
             } catch (err) {
                 console.error('Error submitting applications', err);
                 if (err?.response?.data?.error === 'too_young') {